High-power motor for a body-grip power tool

ABSTRACT

A power tool is provided including a housing having a grip portion with a grip circumference of smaller than or equal to approximately 120 mm; and a brushless direct-current (BLDC) motor at least partially disposed within the grip portion of the housing and configured to output a maximum power output of at least 450 watts. The motor includes a stator including a stator core and stator windings; and a rotor rotatably received within the stator and including a rotor shaft extending along a longitudinal axis and a series of permanent magnet rings mounted sequentially along the longitudinal axis and surrounding the rotor shaft, each permanent magnet including a plurality of magnetic poles.

RELATED APPLICATION

This patent application claims the benefit of U.S. Provisional PatentApplication No. 63/144,802 filed Feb. 2, 2021, and U.S. ProvisionalPatent Application No. 63/266,197 filed Dec. 30, 2021.

FIELD

This disclosure relates to a brushless motor assembly for a rotary tool,and particularly to a compact brushless motor assembly for use in agripping portion of a body grip power tool.

BACKGROUND

Brushless direct-current (DC) motors have been used in power toolapplications for over a decade. While BLDC motors provide many size andpower output advantages over universal and permanent magnet DC motors,it is always desired to manufacture more compact motors while providingthe same or higher power output. While known brushless DC motor designsare capable of outputting high power from a DC power source such as abattery pack to perform many power tool applications such as grinding,cutting, drilling, etc., such motors typically have a diameter greaterthan or equal to 40 mm, making them unsuitable for placement in agripping handle of a power tool.

U.S. Pat. No. 8,816,544 is an example of a brushless motor for agrinding tool sized to be received within a gripping portion of thetool. However, this motor uses an alternating-current (AC) power sourceand is incapable of producing the same output levels from asmaller-voltage DC power source. Further, the motor utilizes a segmentedstator design to form the stator windings, which is expensive and proneto high noise and vibration in high torque applications. What is neededis a brushless DC motor formed of a single-piece stator and including asmall diameter, yet capable of producing a high power output needed forpower tool applications.

SUMMARY

According to an embodiment of the invention, a power tool is providedincluding a housing having a grip portion with a grip circumference ofsmaller than or equal to approximately 120 mm; and a brushlessdirect-current (BLDC) motor at least partially disposed within the gripportion of the housing and configured to output a maximum power outputof at least 450 watts. The motor includes a stator including a statorcore and stator windings; and a rotor rotatably received within thestator and including a rotor shaft extending along a longitudinal axisand a series of permanent magnet rings mounted sequentially along thelongitudinal axis and surrounding the rotor shaft, each permanent magnetincluding a plurality of magnetic poles.

In an embodiment, the rotor includes an outer diameter in the range ofapproximately 13 mm to 16 mm and a length that is at least 1.4 timesgreater than the outer diameter.

In an embodiment, the rotor further comprises a plurality of rotor coresegments securely mounted in series on the rotor shaft, the permanentmagnet rings being respectively mounted on the rotor core segments.

In an embodiment, each rotor core segment is provided with at least twoannular alignment members including flexible material mounted proximatetwo ends of the rotor core segment between the rotor core segment andthe corresponding permanent magnet ring.

In an embodiment, each rotor core segment includes annular grooves,wherein an adhesive material is disposed within the annular grooves forretention of the corresponding permanent magnet ring.

In an embodiment, the permanent magnet rings are securely mounteddirectly on the rotor shaft.

In an embodiment, the rotor shaft includes a stepped constructionincluding a first portion surrounded by the magnet rings and having afirst diameter, and a second portion not surrounded by the magnet ringsand having a second diameter, wherein the first diameter is greater thanthe second diameter.

In an embodiment, a rotor bearing is mounted on the second portion ofthe rotor shaft, and a circuit board is electrically coupled to thestator windings and includes conductive traces facilitatinginterconnections between the stator windings. In an embodiment, therotor bearing is located between the permanent magnet rings and thecircuit board along the longitudinal axis.

In an embodiment, a front bearing is mounted on the rotor shaft forwardof the rotor assembly.

According to an embodiment of the invention, a power tool is providedincluding a housing and a brushless direct-current (BLDC) motor disposedwithin the housing. The motor includes a stator including a stator coreand stator windings; and a rotor rotatably received within the statorand including a rotor shaft extending along a longitudinal axis andpermanent magnets. The rotor shaft includes a stepped constructionincluding a first portion inside the stator assembly having a firstdiameter and a second portion outside the stator assembly having asecond diameter. The first diameter is greater than the second diameterand the permanent magnets are mounted directly on the first portion ofthe rotor shaft.

In an embodiment, a magnet ring integrally is provided that includes thepermanent magnets. The magnet ring has an inner diameter that isapproximately equivalent to the first diameter of the rotor shaft so asto be securely mounted on the first portion of the rotor shaft.

In an embodiment, the magnet ring comprises a plurality of magnet ringsmounted in series on the first portion of the rotor shaft.

In an embodiment, a rotor bearing is mounted on the second portion ofthe rotor shaft, and a circuit board is electrically coupled to thestator windings. The circuit board includes conductive tracesfacilitating interconnections between the stator windings, and the rotorbearing is located between the permanent magnet rings and the circuitboard.

In an embodiment, a sense magnet is mounted on the second portion of therotor shaft, and the circuit board includes Hall sensors in magneticinterface with the sense magnet.

According to an embodiment of the invention, a power tool is providedincluding a housing and a brushless direct-current (BLDC) motor disposedwithin the housing. The motor includes a stator including a stator coreand stator windings; a rotor rotatably received within the stator andincluding a rotor shaft extending along a longitudinal axis andpermanent magnets; and a bearing bridge including a center pocket formedaround the rotor shaft. A rotor bearing mounted on the rotor shaft issecurely received within the center pocket. A circuit board iselectrically coupled to the stator windings and includes conductivetraces facilitating interconnections between the stator windings. Therotor bearing is located between the permanent magnets and the circuitboard along the longitudinal axis.

In an embodiment, the motor further includes an end insulator configuredto electrically insulate the stator core from the stator windings andincluding an annular body extending away from the stator core. Thebearing bridge is received at least partially within the end insulator.

In an embodiment, the stator windings are wound from a continuous magnetwire having cross-over portions extending between the adjacent statorwindings, where the cross-over portions are guided in contact with theend insulator to be electrically coupled to the circuit board. In anembodiment, a radial plane formed through the rotor bearing intersectsthe cross-over portions.

In an embodiment, the motor further includes stator terminals mounted onthe end insulator and oriented circumferentially outward of an end ofthe bearing pocket. The stator terminals include first portions arrangedto receive the cross-over portions of the magnet wire and secondportions arranged to be secured to the circuit board to electricallycouple the cross-over portions of to the circuit board.

In an embodiment, a radial plane formed through the rotor bearingintersects the annular body of the end insulator.

In an embodiment, the motor further includes a sense magnet mounted onthe second portion of the rotor shaft, where the circuit board includesHall sensors in magnetic interface with the sense magnet.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of this disclosure in any way.

FIG. 1 depicts a perspective view of a power tool including a brushlessDC (BLDC) motor, according to an embodiment;

FIG. 2 depicts a perspective view of a BLDC motor, according to anembodiment;

FIG. 3 depicts a cross-sectional view of the BLDC motor, according to anembodiment;

FIG. 4 depicts an axial view of a stator assembly of the BLDC motorduring a winding process, according to an embodiment;

FIG. 5 depicts a perspective view of a winding nozzle for winding thestator assembly, according to an embodiment;

FIG. 6 depicts a cross-sectional view of the winding nozzle, accordingto an embodiment;

FIG. 7 depicts a partially exploded view of a rear end of the BLDCmotor, according to an embodiment;

FIG. 8 depicts a perspective view of the rear end of the BLDC motor,according to an embodiment;

FIG. 9 depicts a partially exploded view of the rear end of the BLDCmotor and a circuit board, according to an embodiment;

FIG. 10 depicts a perspective view of rear end of the motor without thecircuit board, according to an embodiment;

FIG. 11 depicts a perspective view of a terminal slug, according to anembodiment;

FIG. 12 depicts a zoomed-in cross-sectional view of the rear end of themotor including a terminal slug, according to an embodiment;

FIG. 13 depicts a perspective view of the stator assembly of the BLDCmotor, according to an embodiment;

FIG. 14 depicts a partially exploded view of the rear end of the statorassembly including stator terminals, according to an embodiment;

FIGS. 15A and 15B depict front and rear views of a stator terminalmounted on a routing insulator of the stator assembly, according to afirst embodiment;

FIGS. 16A and 16B depict front and rear views of a stator terminalmounted on a routing insulator, according to a second embodiment;

FIGS. 17A and 17B depict front and rear views of a stator terminalmounted on a routing insulator, according to a third embodiment;

FIG. 18 depicts a front view of a stator terminal mounted on a routinginsulator, according to a fourth embodiment;

FIGS. 19A and 19B depict front and rear views of a stator terminalmounted on a routing insulator, according to a fifth embodiment;

FIG. 20 depicts a front view of a stator terminal mounted on a routinginsulator, according to a sixth embodiment;

FIG. 21A depicts a partial perspective view of a rotor assembly of theBLDC motor, according to an embodiment;

FIG. 21B depicts an exploded view of a magnet ring and a rotor core ofthe rotor assembly, according to an embodiment;

FIG. 22A depicts a partial exploded view of a magnet ring and a rotorcore segment, further provided with two alignment members, according toan embodiment;

FIG. 22B depicts a side partial view of the rotor core segment providedwith the alignment members, according to an embodiment;

FIG. 23A depicts partial view of a rotor assembly includingsurface-mount magnet retention features mounted on the rotor shaft,according to an embodiment;

FIG. 23B depicts a partial view of the rotor assembly further providedwith surface-mounted permanent magnets, according to an embodiment;

FIG. 23C depicts a perspective view of the rotor assembly furtherprovided with sleeves and rotor end caps for magnet retention, accordingto an embodiment;

FIG. 24A depicts a depicts a perspective view of the rotor assemblyprovided with a single sleeve, according to an alternative embodiment;

FIG. 24B depicts a depicts a perspective view of the rotor assemblyprovided with an alternative single sleeve, according to an alternativeembodiment;

FIG. 24C depicts a depicts a perspective view of the rotor assemblyprovided with two bushings instead of the rotor end caps above,according to an alternative embodiment;

FIG. 24D depicts a depicts a perspective view of the rotor assemblyprovided with alternative sleeves designed to be joined with the rotorend caps 292, according to an alternative embodiment;

FIG. 25 depicts a perspective view of a BLDC motor, according to analternative embodiment of the invention;

FIG. 26 depicts a perspective cross-sectional view of the BLDC motor,according to an embodiment;

FIG. 27 depicts a side cross-sectional view of the BLDC motor, accordingto an embodiment;

FIG. 28 depicts a side perspective view of a stator assembly of the BLDCmotor, according to an embodiment;

FIG. 29 depicts another side perspective view of the stator assembly,according to an embodiment;

FIG. 30 depicts a side perspective view of a routing insulator of thestator assembly, according to an embodiment;

FIG. 31 depicts another side perspective view of the routing insulator,according to an embodiment;

FIG. 32 depicts a partially exploded view of the rear end of the statorassembly including stator terminals, according to an embodiment;

FIG. 33 depicts a partial view of the rear end of the stator assemblyafter the winding process, according to an embodiment;

FIG. 34 depicts a cross-sectional angular view of the rear end of thestator 310 after the winding and fusing processes, according to anembodiment;

FIG. 35 depicts a rear axial view of the stator assembly 310 after thewinding process and fusing processes, according to an embodiment;

FIG. 36 depicts a partially exploded perspective view of a rear bearingbridge and the stator assembly, according to an embodiment;

FIG. 37 depicts a perspective view of the rear bearing bridge mountedinside a routing insulator of the stator assembly, according to anembodiment;

FIG. 38 depicts an angular cross-sectional view of the rear bearingbridge mounted inside the routing insulator, according to an embodiment;

FIG. 39 depicts a radial cross-sectional view of the rear bearing bridgemounted inside the routing insulator, according to an embodiment;

FIG. 40 depicts a partial perspective view of the stator assembly priorto assembly of retaining insert members, according to an embodiment;

FIG. 41 depicts a partial zoomed-in view of the stator assemblyincluding one retaining insert member, according to an embodiment;

FIG. 42 depicts a partial zoomed-in view of the stator assemblycross-sectioned along a radial plane, according to an embodiment;

FIG. 43 depicts a cross-sectional perspective view similar to FIG. 38,additionally provided with retaining insert members, according to anembodiment;

FIG. 44 depicts a perspective exploded view of a circuit board assemblyand the stator assembly, according to an embodiment;

FIG. 45 depicts a perspective view of the circuit board assembly mountedonto the stator assembly, according to an embodiment;

FIG. 46 depicts a partially exploded perspective view of the circuitboard assembly relative to the rear bearing bridge, according to anembodiment;

FIG. 47 depicts a perspective view of the circuit board assembly mountedand the stator assembly highlighting air inlets, according to anembodiment;

FIG. 48 depicts a partial perspective view of the stator assembly beingreceived through an end of a motor can of the BLDC motor, according toan embodiment;

FIG. 49 depicts a partial perspective view of the motor can with thestator assembly received therein, according to an embodiment;

FIG. 50 depicts a partial exploded view of a rotor assembly and a frontbearing bridge of the BLDC motor, according to an embodiment;

FIG. 51 depicts another partial exploded view of the rotor assembly andthe front bearing bridge, according to an embodiment;

FIG. 52 depicts a partially exploded view of the front end of the motorcan and the front bearing bridge including a compression ring, accordingto an embodiment;

FIG. 53 depicts a zoomed-in cross-sectional view of the front end of themotor can prior to fastening the front bearing bridge, according to anembodiment;

FIG. 54 depicts a zoomed-in cross-sectional view of the front end of themotor can after fastening the front bearing bridge, according to anembodiment;

FIG. 55 depicts a partial perspective view of the motor can and thecompression ring, according to an embodiment;

FIG. 56 depicts a partial perspective view of the motor can with thecompression ring received therein, according to an embodiment;

FIG. 57 depicts a perspective view of BLDC motor houses within aclamshell housing instead of a motor can, according to an embodiment;

FIG. 58 depicts a partially exploded view of the clamshell housingaround the BLDC motor, according to an embodiment;

FIG. 59 depicts another partially exploded view of the clamshell housingaround the BLDC motor, according to an embodiment;

FIG. 60 depicts an exploded view of the BLDC motor components and theclamshell housing, according to an embodiment;

FIG. 61 depicts a partially exploded view of a front end of theclamshell housing and the motor, according to an embodiment;

FIG. 62 depicts another partially exploded view of the front end of theclamshell housing and the motor, according to an embodiment;

FIG. 63 depicts a partially exploded view of a rear end of the clamshellhousing and the motor, according to an embodiment;

FIG. 64 depicts another partially exploded view of the rear end of theclamshell housing and the motor, according to an embodiment;

FIG. 65 depicts a partially exploded side cross-sectional view of therear end of the clamshell housing and the motor, according to anembodiment;

FIG. 66 depicts a perspective view of a power tool including a BLDCmotor, according to an alternative embodiment of the invention;

FIG. 67 depicts a cross-sectional view of the power tool, according toan embodiment;

FIG. 68 depicts a top view of the power tool, according to anembodiment;

FIG. 69 depicts a perspective view of the BLDC motor, according to anembodiment;

FIG. 70 depicts a side cross-sectional view of the BLDC motor, accordingto an embodiment;

FIG. 71 depicts a perspective cross-sectional view of the BLDC motor,according to an embodiment;

FIG. 72 depicts a perspective view of the rotor assembly of the BLDCmotor, according to an embodiment;

FIG. 73 depicts a partial exploded view of a front end of the motor canand a motor adaptor, according to an embodiment;

FIG. 74 depicts a partial exploded view of a rear end of a statorassembly of the BLDC motor including a rear bearing bridge, according toan embodiment;

FIG. 75 depicts a perspective view of the rear end of the rear bearingbridge mounted onto the stator assembly, according to an embodiment;

FIG. 76 depicts a zoomed-in cross-sectional view of the rear end of themotor assembly, according to an embodiment;

FIG. 77 depicts a perspective view of a routing insulator disposed atthe end of the stator assembly, according to an alternative embodiment;

FIG. 78 depicts a perspective view of a circuit board mounted on therouting insulator, according to an embodiment;

FIG. 79 depicts a perspective view of a circuit board mounted on arouting insulator of a stator assembly, according to an alternativeembodiment; and

FIG. 80 depicts a partial cross-sectional view of the circuit board andthe routing insulator, according to an embodiment.

DETAILED DESCRIPTION

The following description illustrates the claimed invention by way ofexample and not by way of limitation. The description clearly enablesone skilled in the art to make and use the disclosure, describes severalembodiments, adaptations, variations, alternatives, and uses of thedisclosure, including what is presently believed to be the best mode ofcarrying out the claimed invention. Additionally, it is to be understoodthat the disclosure is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. The disclosure iscapable of other embodiments and of being practiced or being carried outin various ways. Also, it is to be understood that the phraseology andterminology used herein is for the purpose of description and should notbe regarded as limiting.

FIG. 1 depicts a perspective view of a power tool 10 including anelongate housing 12 that houses a brushless direct-current (BLDC) motor100, a gear case 14 mounted forward of the housing 12, and a batteryreceptacle 16 formed at the foot of the housing 12 opposite the gearcase 14. In this view, the housing 12 is made of a pair of clamshells,one of which is removed to expose the BLDC motor 100 and associatedcomponents disposed within the housing 12, according to an embodiment.

In an embodiment, battery receptacle 16 is configured to receive aremovable and rechargeable power tool battery pack therein. The batterypack, not shown in this figure, may be, for example a lithium-ionbattery pack having a nominal voltage of 18V.

In an embodiment, power tool 10 further includes a trigger assembly 18mounted on the housing 12 and includes a paddle switch 20 engageable bya user and a switch assembly 22 disposed within the housing 12. In anembodiment, switch assembly 22 may include a mechanical contact switch,a logic switch, or a combination thereof, arranged to activate ordeactivate supply of power from the battery pack.

In addition, in an embodiment, power tool 10 includes a control module24, which in this example is disposed near the battery receptacle 16. Inan embodiment, control module 24 includes a programmable controller,such as a microcontroller device, not shown in this figure, mounted on aprinted circuit board. The controller includes code that controls supplyof electric power to the motor according to various criteria, such asload, speed, and power requirements. In an embodiment, control module 24may further include a series of power switches, also not shown,configured as a three-phase inverter circuit, controlled by thecontroller for driving the motor 100. Details of the controller andpower switcher are beyond the scope of this disclosure. Reference ismade, by way of example, to U.S. Pat. Nos. 10,680,494; 10,615,733; and10,693,344, all of which are incorporated herein by reference in theirentireties, as various examples of motor control and driveconfigurations.

In an embodiment, the power tool 10 is an angle grinder by way ofexample, though it should be understood that the principles describedherein may be utilized in various other power tools such as a cutouttool, a polisher, a wrench, a drill, an impact driver, a hammer drill, acircular saw, a reciprocating saw, a band saw, a nailer, etc.

In an embodiment, the gear case 14 receives a motor shaft that isrotatable with the motor 100 and includes a series of gears and supportsan output spindle driven In an embodiment, the output spindle may beoriented perpendicularly to the motor shaft. In an embodiment, the gearcase 14 may additionally include a spindle lock engageable by a user toprevent rotation of the output spindle while the user is mounting agrinding or cutting wheel onto the output spindle. In an embodiment, thegear case 14 may also include a retention flange configured to apply abiasing force to the grinding or cutting wheel for increased security,as described in U.S. patent application Ser. No. 17/412,448 filed onAug. 26, 2021, which is incorporated herein by reference in itsentirety. In an embodiment a guard 26 may be mounted on a collar portionof the gear case 14 around the grinding or cutting accessory.

In an embodiment, the power tool 10 is designed as a body-grip powertool with the housing 12 being sized to fit into a hand grip of a userwith relative ease even in the area around the motor 100. As such, in anembodiment, the housing 12 has a maximum diameter D of approximately 35to 45 mm, preferably approximately 37 to 43 mm, more preferably at most40 mm, around most of the length of the motor 100. In an embodiment,this maximum diameter D is extends along length A of the housing 12,beginning proximate the battery receptacle 16 and a pivoting connectionpoint 28 of a distal end of the paddle switch 20, to a frontal end 30 ofthe housing 12 formed around a fan baffle 32 radially containing a motorfan (not shown) and a front end of the motor 100. In an embodiment, thefront end 26 of the housing 12 includes a larger diameter than theremainder the housing 12 by a factor of approximately 1.7 to 2. Itshould be understood, however, that in some applications, the rear ofthe gear case 14, and thus the front end 26 of the housing 12, include adiameter that is approximately equal to or up to 20% greater than thediameter of the remainder of the housing 12. In an embodiment, thehousing 12 includes a maximum diameter D along at least 80% of theentire length of the motor 100, preferably along at least 85% of theentire length of the motor 100.

FIG. 2 depicts a perspective view of the brushless DC (BLDC) motor 100,according to an embodiment. FIG. 3 depicts a cross-sectional view of themotor 100, according to an embodiment.

In an embodiment, the motor 100 includes a motor housing (or motor can)102 having a substantially cylindrical body and two open ends thatsupports the components of the motor 100 described below. In anembodiment, the motor can 102 may be made of steel or other metal toprovide a reliable mounting structure for the motor components. Themotor 100 further includes a stator assembly 110 and a rotor assembly120 mounted on a rotor shaft 122.

In an embodiment, stator assembly 110 is securely received within theinner diameter of the motor can 102 and includes a stator core 112,which may be formed of a series of laminated steel members, and a seriesof stator windings 114 supported by the stator core 112. In anembodiment, the rotor assembly 120 includes one or more rotor coresegments 124 mounted on the rotor shaft 122 in series, each rotor coresegment 124 supporting a series of permanent magnets or a permanentmagnet ring 126 mounted on its outer surface. In an embodiment, therotor assembly 120 is disposed within the stator assembly 110. As statorwindings 114 are energized in a controlled sequence, the magneticinteraction between the stator windings 114 and the permanent magnets126 causes the rotation of the rotor assembly 120 relative to the statorassembly 110. For details on constructional and operational principlesof the stator and the rotor, reference is made to U.S. Pat. No.10,923,989, and US Patent Publication No. 2021/0194320, both of whichare incorporated herein by reference in their entireties.

In an embodiment, stator assembly 110 further includes a front endinsulator 116 mounted on an axial end of the stator core 112 to insulatethe stator windings 114 from the stator core 122. Specifically, frontend insulator 116 includes a series of teeth corresponding to the teethof the stator core 112, and the stator windings 114 are wound around theteeth of the front end insulator 116 to avoid direct contact with themetal part of the stator core 112. Reference is made to U.S. Pat. No.10,328,566, as an example of a stator end insulator construction.

In addition, stator assembly 110 further includes a rear end insulator160, herein referred to as a routing insulator. Routing insulator 160 ismounted on the other axial end of the stator core 112 opposite the frontend insulator 116, and similarly acts to insulate the stator windings114 from the stator core 122. However, routing insulator 160 has agreater axial length than the front end insulator 116, and it includesfeatures for routing the magnet wire between stator windings 114 andsupporting additional components associated with the stator windings114, as will be described later in detail. In an embodiment, routinginsulator 160 extends beyond the rear axial end of the motor can 102.

In an embodiment, motor 100 additionally includes a front bearingsupport structure (also referred to as front bearing bridge 130), and arear bearing support structure (also referred to as rear bearing bridge)140, mounted on the two axial ends of the motor can 102 adjacent twoends of the stator assembly 110. These features will be described belowin detail.

In an embodiment, the motor 100 has an overall total length B, asdefined from a front end of the front bearing bridge 130 to a rear endof the rear bearing bridge 140, of approximately 100 mm to 130 mm,preferably approximately 110 mm to 120 mm. In an embodiment, the statorassembly 110 has length C, as defined by the length of the stator core112, of approximately 45 mm to 75 mm, preferably approximately 55 mm to65 mm, and more preferably no greater than 60 mm. As such, thedifference between the overall total length B of the motor and thelength C of the stator assembly 110 is approximately 45 mm to 65 mm,preferably approximately 50 mm to 60 mm. In an embodiment, length B isgreater than length C by approximately 52% to 63%

In an embodiment, the motor 100 also has a diameter D′, as defined bythe outer diameter of the motor can 102, of approximately 31 mm to 36mm, preferably approximately 33 mm to 35 mm, preferably no more than 34mm. The stator assembly 110 further includes an outer diameter OD, asdefined by the outer diameter of the stator core 112, of approximately27 mm to 34 mm, preferably approximately 28 mm to 33 mm, preferablyapproximately 29 mm to 32 mm. These dimensions allow for the motor 100to fit into the small girth of the housing 12 of the power tool 10 whileproducing enough power for grinding or cutting applications. In anembodiment, the motor 100 is configured to produce maximum long durationpower output of at least approximately 450 watts.

In an embodiment, the length B of the motor 100 is at leastapproximately 50%, more preferably 55%, and even more preferably 60%, ofthe overall length of the tool housing 12 including frontal end 30 andthe battery receptacle 16.

In an embodiment, stator assembly 110 may include a segmented design,where a series of (for example, six) discrete core segments areseparately wound and then joined together to form the stator core 112.This configuration is particularly suitable for a small-diameter statorassembly 110, where each segment may be wound to the desired number ofturns prior to forming the stator core 112. This configuration, however,has drawbacks associated with cost of manufacturing, reliability, noiseand vibration, and cogging torque.

Alternatively, and preferably, stator core 112 is formed with anon-segmented annular body and a series of inwardly-projecting teeth onwhich the stator windings 114 are wound. Stator core 112 may be asolid-core unit made as a single piece. Alternatively, stator core 112may be made of laminated steel sheets placed together and interlocked toform a uniform body.

A challenge associated with a non-segmented stator core having a smalldiameter of, e.g., 36 mm or less is the winding process of the statorwindings 114, particularly if a high slot fill is needed to produce ahigh power density. The winding process may be particularly challengingwhere the length of the stator is large to compensate for the smallerdiameter.

FIG. 4 depicts an axial view of the stator assembly 110 during thewinding process of the stator windings 114. In this figure, a windingnozzle 170 is provided for winding the stator windings 114, according toan embodiment. FIG. 5 depicts a perspective view of the winding nozzle170. FIG. 6 depicts a cross-sectional view of the winding nozzle alonethe plane A-A.

In an embodiment, the winding nozzle 170 includes a main body 172,details of which are beyond the scope of this disclosure. Main body 172is located outside the body of the stator core 112 during the windingprocess to feed the magnet wire for the winding. The winding nozzle 170further includes a winding arm 174 extending from the main body 172 andsized to fit inside the inner diameter (ID) of the stator assembly 110as defined by the distance between opposing inner teeth 111 of thestator core 112. A nozzle head 176 is disposed at the end of the windingarm 174 that is received within the stator slots for winding the magnetwire to form the stator windings 114.

In an embodiment, as discussed above, the outer diameter (OD) of thestator core 112 is approximately 27 mm to 34 mm, leaving an innerdiameter (ID) of approximately 14 to 17 mm within which the winding arm174 is received and operated. In an embodiment, a radial width (W) ofthe winding arm 174 is approximately less than half the inner opening ofthe stator, i.e., approximately 7 to 8.5 mm. Further, due to the largelength of the stator, in an embodiment, a length of the winding arm 174is greater than approximately 75 mm.

Referring to FIGS. 2 and 3, in an embodiment, the front bearing bridge130 is described herein. In an embodiment, the front bearing bridge 130includes a bearing pocket 132 formed around an outer race of a frontbearing 104 mounted on the rotor shaft 122 that securely supports thefront bearing 104, a series of radial arms 134 that project outwardlyfrom the bearing pocket 132, and an outer ring 136 configured to matewith an end of the motor can 102. In an embodiment, outer ring 136 isform-fittingly received inside the inner surface of the motor can 102 toradially pilot and structurally support the front bearing bridge 130,and therefore the front bearing 104, relative to the motor can 102. Inan embodiment, a radial lip 138 projects outwardly from the outer ring136 in contact with the end surface of the motor can 102.

In an embodiment, a fan 108 is mounted on the rotor shaft 122 via abushing 109 adjacent the front bearing bridge 130. In an embodiment, fan108 may be an axial fan including a series of blades that generate anairflow through the motor can 102. In an embodiment, front bearingbridge 130 is disposed in close enough proximity to act as a baffle forthe fan 108. In an embodiment, fan baffle 32 (FIG. 1) may be provided inaddition to, or integrally with, the front bearing bridge 130, tosupport a larger diameter fan 108 and extend around the outer peripheryof the fan 108.

In an embodiment, the fan 108 includes substantially the same diameteras the stator core 112 and/or the motor can 102. Alternatively, in anembodiment, the fan 108 includes a diameter that is approximately 70% to100% larger than the outer diameter of the motor can 102.

FIG. 7 depicts a partially exploded view of the rear end of the motor100. FIG. 8 depicts a perspective view of the rear end of the motor 100.Referring to these figures, and with continued reference to FIGS. 2 and3, the rear bearing bridge 140 is described herein.

In an embodiment, rear bearing bridge 140 includes a cylindrical bearingpocket 142 formed around an outer race of a rear bearing 106 mounted onthe rotor shaft 122 that securely supports the rear bearing 106. In anembodiment, an annular ring 144 projecting inwardly from the bearingpocket 142 axially engages the rear bearing 106. In an embodiment, aninner annular body 146 extends from the annular ring 144 around therotor shaft 122 in a direction opposite the bearing pocket 142. A sensemagnet 107 mounted on the rotor shaft 122 between the end of the shaft122 and the rear bearing 107 is arranged within the inner annular body146 with an airgap therebetween. The sense magnet 107 has amagnetization orientation that corresponds to the orientation of thepermanent magnet ring 126.

In an embodiment, a radial plate 148 projects radially outwardly from arear end of the inner annular body 146 defining a series of openings 150therein. In an embodiment, an outer annular body 152 extends from theboundary of the radial plate 148 coaxially around the inner annular body146 and the bearing pocket 142 at approximately the same axial length asthe inner annular body 146 and the bearing pocket 142 combined. Theouter annular body 152 includes a series of peripheral openings 154arranged to receive airflow from outside the motor 100. The outerannular body 152 includes a diameter that is substantially equal to thediameter D′ of the motor can 102. In an embodiment, outer annular body152 mates with the rear end of the cylindrical body, preferably forminga flush outer surface. In an embodiment, the rear end of the motor can102 includes an annular lip 103 that is configured to be form-fittinglyreceived inside the front end of the outer annular body 152. Thisarrangement radially pilots and structurally supports the rear bearingbridge 140, and therefore the rear bearing 106, relative to the motorcan 102.

In an embodiment, a circuit board 180 is mounted on the rear end of therear bearing bridge 140 adjacent the radial plate 148. The circuit board180 includes center opening 181 through which the rear end of the rotorshaft 122 is received. The circuit board 180 also includes a series ofholes 182 near its outer periphery corresponding to fasteningreceptacles 156 disposed on the radial plate 148 of the rear bearingbridge 140. Fasteners 184 are received through the holes 182 andfastened into the fastening receptacles 156 to securely support thecircuit board 180 adjacent the radial plate 148.

In an embodiment, the circuit board 180 includes a series of magneticsensors (e.g., Hall elements) 186, only one of which can be seen in FIG.3, disposed around the center opening 181 facing the sense magnet 107 atan equidistant angular orientation. The center opening 181 includes asmaller diameter than the inner annular body 146, allowing exposure ofthe magnetic sensors 186 to the sense magnet 107 along the axialdirection. The magnetic sensors 186 magnetically sense the magnetic fluxof the sense magnet 107 and output positional signals associated withthe rotational position of the rotor assembly 120 accordingly. In anembodiment, a connector 188 is mounted on the rear surface of thecircuit board 180 to output the positional signals, which are receivedvia signal wires (not shown) by the control module 24.

In an embodiment, as described above, a rear end of the routinginsulator 160 extends beyond the rear axial end of the motor can 102.The rear end of the routing insulator 160 is received within the body ofthe outer annular body 152 of the rear bearing bridge 140 such that aradial plane intersecting the rear bearing 106 also intersects therouting insulator 160. In an embodiment, the rear end of the routinginsulator 160 extends approximately to a plane that interests theannular ring 144 of the bearing pocket 142.

In an embodiment, a series of stator terminals 190 are mounted on therouting insulator 160. In an embodiment, the number of stator terminals190 equals the number of stator windings 114. In a three-phase four-polemotor, six stator windings 114 and six stator terminals 190 areprovided. In an embodiment, each stator terminal 190 is provided betweenadjacent windings 114, with cross-over portions 118 of the magnet wirepassing only between adjacent windings 114 coming in contact with thestator terminal 190. The stator terminals 190, as will be describedlater in detail, include tang portions 194 that make electrical contactwith the cross-over portions 118 of the magnet wire, and terminal pins192 that extend axially from the routing insulator 160 through openings150 of the rear bearing bridge 14. The circuit board 180 includes aseries of slots 189 that securely receive the ends of the terminal pins192 of the stator terminals 190. In an embodiment, a series of wires 185are secured to the circuit board 180 to deliver power from the controlmodule 24, via the circuit board 180, to the stator terminals 190. Inaddition, the circuit board 180 the circuit board includes conductiveroutings extending from the slots 189, which electrically connect to thestator terminals 190. In an embodiment, the circuit board 180 may beconfigured to electrically connect the stator terminals 190, and thusthe stator windings 114, in a desired configuration. Specifically, in anembodiment, the circuit board 180 may include conductive routings toconnect opposite stator windings 114 of the same phase in a series orparallel connection. In an embodiment, the circuit board 180 may alsoinclude conductive routings to connect stator windings 114 of differentphases in a wye or a delta connection. Reference is made to U.S.Provisional Application No. 63/129,797 filed Dec. 23, 2020, which isincorporated herein by reference in its entirety, for an example of acircuit board that facilitates interconnections between the statorwindings in this manner.

In an embodiment, to properly align the slots 189 of the circuit boardwith the terminal pins 192 of the stator terminals 190, pilotingfeatures including a tongue 157 and a corresponding groove 187 areprovided on the rear bearing bridge 140 and the circuit board 180respective.

FIG. 9 depicts a partially exploded view of the rear end of the motor100, showing the circuit board 180 at a distance from the rear bearingbridge 140, according to an embodiment. FIG. 10 depicts a perspectiveview of rear end of the motor 100 without the circuit board 180,according to an embodiment.

In an embodiment, as shown here, a series of terminal slugs 200 areprovided around the rear ends of the terminal pins 192 of the statorterminals 190, according to an embodiment. In an embodiment, theterminal slugs 200 are made of insulating material such as rubber orplastic and shaped to form sleeves around terminal pins 192 toelectrically insulate the stator terminals 190 from the rear bearingbridge 140. This arrangement reduces the risk of electrical shortagebetween the stator terminals 190 and other components. Further, in anembodiment, terminal slugs 200 are fitted into openings 150 of the rearbearing bridge 140, thus axially securing the terminal pins 192 of thestator terminals 190 relative to the rear bearing bridge 140. Thisarrangement reduces the risk of the terminal pins 192 from being bentduring the assembly process and ensures proper alignment of the terminalpins 192 with the slots 189 of the circuit board 180.

FIG. 11 depicts a perspective view of a terminal slug 200, according toan embodiment. FIG. 12 depicts a zoomed-in cross-sectional view of therear end of the motor 100, showing the terminal pin 192 of one of thestator terminals 190 received within a corresponding terminal slug 200,according to an embodiment.

In an embodiment, as shown in these figures, each terminal slug 200includes a first portion 202 sized to be form-fittingly received withina corresponding opening 150 of the rear bearing bridge 140. Eachterminal slug 200 further includes a second portion 204 that includes alarger cross-sectional area but shorter axial length than the firstportion 202 and is configured to rest on top of the radial plate 148prior to assembly of the circuit board 180 and be sandwiched between theradial plate 148 of the rear bearing bridge 140 and the circuit board180 after the circuit board 180 is mounted on the rear bearing bridge140. In this manner, terminal slugs 200 also provide a flexible mountingplatform for the circuit board 180. Each terminal slug 200 also includesa slot 206 having a rectangular cross-section that extends through theaxial length of the terminal slug 200 sized to form-fittingly receivethe terminal pins 192 of the stator terminals 190.

Various embodiments of the stator terminals and mounting of the statorterminals to the routing insulator are described herein.

FIG. 13 depicts a perspective view of the stator assembly 110, accordingto an embodiment. FIG. 14 depicts a partially exploded view of the rearend of the stator assembly 110, showing the stator terminals 190 at adistance from the routing insulator 160, according to an embodiment.FIGS. 15A and 15B depict front and rear views of a stator terminal 190mounted on the routing insulator 160, according to an embodiment.

In an embodiment, as described above, the front end insulator 116 andthe routing insulator (i.e., rear end insulator) 160 are mounted on thetwo ends of the stator core 112 prior to winding of the magnet wire toform the stator windings 114. The front end insulator 116 and therouting insulator 160 are respectively provided with tongues 210 and 212that are aligned and received into an axial channel 214 formed in theouter surface of the stator core 112 for proper alignment of the frontend insulator 116 and the routing insulator 160 relative to the statorcore 112.

In an embodiment, the routing insulator 160 includes a series ofrecessed region 162 at its rear surface. In addition, the routinginsulator 160 includes several pairs of retaining legs 164 and 166projecting axially-rearwardly from rear surface on two sides of eachrecessed region 162.

In an embodiment, each stator terminal 190 includes a main body 196sized to be securely received within the gap formed between thecorresponding retaining legs 164 and 166. The tang portion 194 of theeach stator terminal 190 extends from the main body 196 and folded overthe main body at an angle of approximately 30 to 60 degrees. Theterminal pin 192 of each stator terminal 190 extends from one side ofthe main body 196 adjacent the tang portion 194. In an embodiment, asecond leg 198 extends from the other side of the motor body 196. In anembodiment, second leg 198 is significantly smaller in height and sizethan the terminal pin 192. In an embodiment, the tang portion 194extends from an edge of the main body 196 between the terminal pin 192and the second leg 198.

In an embodiment, at least the retaining legs 164 includeaxially-extending grooves 168 facing the recessed regions 162. In anembodiment, during the assembly process of each stator terminal 190, thesecond leg 198 is slidingly received into the groove 168 of theretaining leg 164. In an embodiment, the side of the main body 196 fromwhich the terminal pin 192 extends encounters, or is received within agroove of, the retaining leg 166. In an embodiment, the tang portions194 of the stator terminals 190 is received within the recessed portions162.

In an embodiment, as the magnet wire is wound to form respective statorwindings 114, the cross-over portions 118 of the magnet wire passingfrom the wound stator winding 114 to the next (i.e., to be wound) statorwinding 114 are guided to the rear end of the routing insulator 160 andpassed along the rear end of the routing insulator 160 between axialsides of the recessed regions 162. In an embodiment, as the statorterminals 190 are mounted on the routing insulator 160, folded regionsof the tang portions 194 capture the cross-over portions 118 of themagnet wire. After the stator terminals 190 are fully secured, the tangportions 194 are radially pressed through the recessed regions 162against the main bodies 196. The wire insulator parts of the cross-overportions 118 are removed and the conductive parts are of the cross-overportions 118 are electrically connected to the tang portions 194 of thestator terminals 190. This may be done via fusing, wire stripping,welding, soldering, or a combination thereof. Pressing of the tangportions 194 against the main body 196 ensures that no part of thestator terminals 190 projects radially outwardly beyond the outercircumference of the routing insulator 160.

FIGS. 16A through 21B depict various configurations of the statorterminal, according to alternative embodiments.

FIGS. 16A and 16B depict front and rear perspective views of a statorterminal 220, according to an embodiment. In this embodiment, therouting insulator 160 includes a series of mounting projections 230 foreach stator terminal 220. Each stator terminal 220 includes a main body226, a terminal pin 222 extending from one end of the main body 226 awayfrom the routing insulator 160, and a tang portion 224 extending from anopposite end of the main body 226 and folded angularly over the mainbody 226. Two side legs 228 extend from sides of the main body 226 andin the direction of the routing insulator 160. The side legs 228 includehooks 229 that cooperatively wrap around the sides of the mountingprojection 230 to secure the stator terminal 220 to the mountingprojection 230. During the assembly process, the tang portion 224captures the cross-over portion of the magnet wire (not shown) and ispressed against the main body 226.

FIGS. 17A and 17B depict front and rear perspective views of a statorterminal 240, according to another embodiment. In this embodiment, therouting insulator 160 includes a series of mounting projections 250 foreach stator terminal 240, each mounting projection 250 including twoarms 252 defining an opening 254 therebetween. Each stator terminal 240includes a main body 246, a terminal pin 242 extending from a distal endof the main body 246 away from the routing insulator 160, and a tangportion 244 extending from an opposite end of the main body 246 andfolded angularly over the main body 246 in alignment with the opening254. Two side legs 248 extend from the distal end of the main body 246on two sides of the terminal pin 242 and are folded over the two arms252 of the mounting projection 250. The arms 252 include snappingportions 254 arranged to be received within corresponding holes 249 ofthe side legs 248 to secure the stator terminal 240 to the mountingprojection 250. During the assembly process, the tang portion 244captures the cross-over portion of the magnet wire (not shown) and ispressed into the opening 254 against the main body 246.

FIG. 18 depicts a front perspective view of the stator terminal 240,according an alternative embodiment. In this embodiment, arms 252 of themounting projection 250 include upper cantilever snap beams 270. Theside legs 248 of the stator terminal 240 include upper openings 272through which the upper cantilever snap beams 270 are received to make asnap-fit connection between the mounting projection 250 and the statorterminal 240.

FIGS. 19A and 19B depict front and rear perspective views of a statorterminal 260, according to an embodiment. In this embodiment, therouting insulator 160 includes the same mounting projections 250 asdescribed above, each mounting projection 250 including two arms 252defining an opening 254 therebetween. Each stator terminal 260 includesa main body 266, a terminal pin 262 extending from a distal end of themain body 246 away from the routing insulator 160 off-center from thecenter axis of the main body 266, and a tang portion 264 extending fromthe same distal end the main body 246 along the center axis and adjacentthe terminal pin 262. In an embodiment, a second leg 267 extends from anopposite end of the main body 266 along the center axis and is receivedin alignment with the opening 254. The tang portion 264 is foldedangularly over the main body 266 in alignment with the opening 254. Twoside legs 268 extend from the sides of the main body 266 and formopposite hooks around the two arms 252 of the mounting projection 250.The arms 252 include snapping portions 254 arranged to be receivedwithin corresponding holes 269 of the side legs 268 to secure the statorterminal 260 to the mounting projection 250. During the assemblyprocess, the tang portion 264 captures the cross-over portion of themagnet wire (not shown) and is pressed into the opening 254 against thesecond leg 267. Since the folded angle of the tang portion 264 faces therouting insulator 160, this embodiment provides the advantage ofallowing the cross-over portion of the magnet wire to be directlyreceived within the tang portion 264 as the stator terminal 260 ismounted on the routing insulator 160.

FIG. 20 depicts a front perspective view of the stator terminal 260,according an alternative embodiment. In this embodiment, arms 262 of themounting projection 260 include upper cantilever snap beams 274. Theside legs 268 of the stator terminal 260 make a snap-fit connection withthe cantilever snap beams 274 to secure the mounting projection 250 andthe stator terminal 260.

Rotor assembly 120 is described herein with reference to FIGS. 21-25,according to an embodiment.

FIG. 21A depicts a partial perspective view of the rotor assembly 120,according to an embodiment. FIG. 21B depicts an exploded view of a setof permanent magnet ring 126 and rotor core segment 124, according to anembodiment.

In an embodiment, the rotor assembly has an outer diameter in the rangeof approximately 13 mm to 16 mm, and a length that greater than or equalto the length of the stator core 112, preferably at least approximately2 mm to 5 mm greater than the length of the stator core 112, i.e.,approximately at least 33 mm long. Accordingly, the ratio of the rotorlength to its diameter is at least approximately 3:1, preferablyapproximately greater than 4:1. To accommodate such a high length todiameter ratio, in an embodiment, rotor assembly 120 includes a seriesof rotor core segments 124, three rotor core segments 124 in thisexample, mounted on the rotor shaft 122. Each rotor core segment 124 hasa surface-mounted permanent magnet ring 126 disposed on its outersurface. Each permanent magnet ring 126 is cylindrical in shape, with aninner diameter that is slightly in diameter than the outer diameter ofthe rotor core segment 124 so it can be slidingly mounted to the outersurface of the rotor core segment 124. Each permanent magnet ring 126 ismagnetized with a N-S-N-S orientation. In an embodiment, a layer isadhesive is applied between the outer surface of the rotor core segment124 and the inner surface of the permanent magnet ring 126. In anembodiment, a series of annular grooves 127 is disposed in the outersurface of the rotor core segment 124 to aid in retention of theadhesive.

FIG. 22A depicts a partial exploded view of a permanent magnet ring 126and a rotor core segment 124, further provided with two alignmentmembers 128, according to an embodiment. FIG. 22B depicts a side partialview of the rotor core segment 124 provided with the alignment members128, according to an embodiment.

In this embodiment, to ensure that each permanent magnet ring 126 isaligned co-axially with the corresponding rotor core segment 124, twoalignment members 128 are disposed on two ends of each rotor coresegment 124. Alignment members 128 may be made of rubber or plasticmaterial. In an embodiment, alignment members 128 are plastic tapeswrapped around the two ends of the rotor core segment 124. The outerdiameter of the alignment members 128 corresponds to the inner diameterof the permanent magnet rings 126 to ensure a tight fit between thepermanent magnet rings 126 and the rotor core segments 124. In anembodiment, adhesive is applied to the outer surface of the rotor coresegments 124 between the alignment members 128.

The above-described embodiments are directed to rotor assembly 120including permanent magnet ring 126, or series of permanent magnet rings126, mounted on rotor shaft 122. Permanent magnet ring 126 may be madeof any magnetic material, including rare-earth magnetic material. Magnetrings 126 may be constructed using a hot extrusion process, wherebonding agent is mixed with magnetic material, and a die-processing isused at elevated temperature to align the grains of the magneticmaterial in the direction of the magnetization while forming the magnetin the desired shape and size. This construction has many advantages andis particularly suitable for a small diameter rotor as described above.In particular, this magnet construction is more suitable an embeddedmagnet design for a small diameter rotor construction. In an embodiment,where the ID of the stator is approximately in the range of 14 to 17 mm,the outer diameter of the rotor assembly 120 may be in approximately inthe range of 13 mm to 16 mm, the magnet ring construction is far moresuitable than an embedded magnet construction. Further, since the magnetrings 126 and rotor core segments 126 are mounted in sequence, anydesired rotor length is achievable. However, due to the presence of ahigh concentration of bonding agent, the hot extrusion process typicallyprovides magnet rings having a magnetic rating of, for example, 48 orless.

In an alternative embodiment, as described below, rotor assembly use inmotor 100 may include surface-mounted discrete permanent magnets mountedon the outer surface of a rotor core. Discrete permanent magnets may besintered magnets capable of higher magnetic ratings of, e.g., rating of56 or higher.

FIG. 23A depicts partial view of a rotor assembly 280 including a rotorcore 284 including surface-mount magnet retention features mounted onthe rotor shaft 282, according to an embodiment. In an embodiment, rotorcore 284 is a lamination stack having a substantially cylindrical outersurface and a series of guide rails 286 projecting radially outwardlyand extending longitudinally along the outer surface. In a three-phasebrushless motor including four permanent magnets, four guide rails 286are provided at 90 degree intervals. In an embodiment, the cylindricalouter surface of the rotor core 284 has an outer diameter ofapproximately 11 to 14 mm.

FIG. 23B depicts a partial view of the rotor assembly 280, furtherprovided with surface-mounted permanent magnets 288 mounted on the outersurface of the rotor core 284, according to an embodiment. In anembodiment, each magnet 288 is arcuate shaped extending axially alongthe full length of the rotor core 284 and circumferentially along lessthan 90 degrees of the circumference of the rotor core 284. Thepermanent magnets 288 are received between the guide rails 286. In anembodiment, guide rails 286 may be include side ridges that engage thepermanent magnets 288, thus allowing axial insertion of the permanentmagnets 288 between the guide rails 286 while providing radial retentionfor the permanent magnets 288 on the rotor core 284 while.

FIG. 23C depicts a perspective view of the rotor assembly 280, furtherprovided with sleeves 290 and rotor end caps 292, according to anembodiment. In an embodiment, sleeves 290 are metallic cylindricalbodies mounted on permanent magnets 288 to hold and radially support thepermanent magnets 288 against the outer surface of the rotor core 284.In an embodiment, rotor end caps 292 are mounted on the rotor shaft 282to axially restrain the permanent magnets 288.

In an embodiment the guide rails 286 project radially outwardly so as tocircumferentially align with approximately the outer surfaces of thepermanent magnets 288 and make contact with the inner surfaces of thesleeves 290. The added structural support provided by the sleeves 290assists the guide rails 286 in maintaining concentricity and theretention force required to retain the permanent magnets 288. Inaddition, this arrangement adds additional metal between the permanentmagnets 288 along the circumferential direction and has shown to improveefficiency and power output by approximately 1% to 2%.

FIG. 24A depicts a depicts a perspective view of the rotor assembly 280,provided with a single sleeve 294, according to an alternativeembodiment. In this embodiment, the sleeve 294 is singularly provided inplace of two separate sleeves 290. In an embodiment, sleeve 294 may beshorter in length than the stator core 284 and may be aligned with acenter portion of the rotor core 284 along the axial direction.

FIG. 24B depicts a depicts a perspective view of the rotor assembly 280,provided with an alternative single sleeve 295, according to analternative embodiment. In this embodiment, the sleeve 295 aloneprovided for radial retention of the permanent magnets 288. In anembodiment, sleeve 295 is approximately the same length as the rotorcore 284, therefore extending between the two rotor end caps 292.

FIG. 24C depicts a perspective view of the rotor assembly 280, providedwith sleeves 290 and two bushings 293 instead of the rotor end caps 292above, according to an alternative embodiment. In this embodiment, thebushings 293 include clocking features 296 formed as recesses throughits outer body. During the assembly process, the clocking features 296are axially aligned with the permanent magnets 288, making it easier tolater align the sense magnet with the rotor assembly 280.

FIG. 24D depicts a perspective view of the rotor assembly 280, providedwith alternative sleeves 298 designed to be joined with the rotor endcaps 292, according to an alternative embodiment. In this embodiment,sleeves 298 include radial walls 299 that engage the outer ends of therotor end caps 292. The radial walls 299 may be securely joined with therotor end caps 292 or the rotor core 284 via, for example, soldering orwelding.

An alternative motor construction is described herein, according to anembodiment.

FIG. 25 depicts a perspective view of a BLDC motor 300, according to anembodiment. FIG. 26 depicts a perspective cross-sectional view of theBLDC motor 300, according to an embodiment. FIG. 27 depicts a sidecross-sectional view of the BLDC motor 300, according to an embodiment.FIGS. 26 and 27 are made along two different cross-section planes toprovide a more comprehensive illustration of the motor 300 components.

In an embodiment, the motor 300 includes a motor housing (or motor can)302 having a substantially cylindrical body and two open ends thatsupports the components of the motor 300 described below. In anembodiment, the motor can 302 may be made of steel or other metal toprovide a reliable mounting structure for the motor components. Themotor 300 further includes a stator assembly 310 and a rotor assembly320 mounted on the rotor shaft 322.

In an embodiment, stator assembly 310 and rotor assembly 320fundamentally include many of the same features as stator assembly 110and rotor assembly 120 described above. Stator assembly 310 is securelyreceived within the inner diameter of the motor can 302 and includes astator core 312, which may be formed of a series of laminated steelmembers and includes a series of stator teeth 311 projecting radiallyinwardly from the annular body of the stator core 312, and a series ofstator windings 314 supported by the stator core 312.

In an embodiment, the rotor assembly 320 includes a series of permanentmagnets or permanent magnet rings 326. In an embodiment, the rotorassembly 320 is disposed within the stator assembly 310. As statorwindings 314 are energized in a controlled sequence, the magneticinteraction between the stator windings 314 and the permanent magnets326 causes the rotation of the rotor assembly 320 relative to the statorassembly 310.

In an embodiment, motor 300 includes a straight rotor shaftconstruction, with rotor shaft 322 having a uniform diameter frombeginning to end. In an embodiment, a series of rotor core segments 324,as previously described with reference to FIGS. 21-24, are securelymounted on the rotor shaft 322. Further, a series of permanent magnetrings 326 are surface-mounted on the rotor core segments 324 in magneticinteraction with the stator windings 314.

In an embodiment, a sense magnet 307 is mounted on the rotor shaft 322between the rear end of the shaft 322 and the rear bearing 306. In anembodiment, the sense magnet 307 has a magnetization orientation thatcorresponds to the orientation of the permanent magnet rings 326.

In an embodiment, stator assembly 310 further includes a front endinsulator 316 and a rear end insulator 360 (also referred to as routinginsulator 360) mounted on opposing axial ends of the stator core 312 toinsulate the stator windings 314 from the stator core 322. Front endinsulator 316 includes many of the same features as front end insulator116 previously described and is provided primarily to electricallyinsulator the stator core 316 from the stator windings 314 at the frontend of the motor. Similarly, routing insulator 360 includes many of therouting insulator 160 previously described and is provided primarily toelectrically insulate the stator core 312 from the stator windings 314at the rear end of the motor. Routing insulator 360 is smaller in lengththan previously-described routing insulator 160. Details of front endinsulator 316 and routing insulators 360 are described later in detail.

In an embodiment, routing insulator 360 supports a series of statorterminals 390 projecting along the axial direction away from the statorassembly 310.

In an embodiment, a circuit board assembly 380 including a circuit board382 is mounted on the rear end of the routing insulator 360 inelectrical contact with the stator terminals 390. The circuit board 382includes many of the same features as circuit board 180 described above.The circuit board 382 includes a center opening 384 through which (orclose to which) the rear end of the rotor shaft 322 is positioned. Aseries of magnetic sensors (not shown) are mounted on the circuit board382 in magnetic interface with the sense magnet 307. The circuit board382 further includes peripheral slots 386 that receive the statorterminals 390 from the routing insulator 360 and includes conductiveroutings to connect the stator windings 314 of different phases in a wyeor a delta connection. In an embodiment, a series of power wires 389 forsupplying electric power to the motor 300, and a series of signal wires388 for communication between a microcontroller and the magneticsensors, are secured to the circuit board assembly 380. In anembodiment, circuit board assembly 380 includes an overmold structure381 formed around at least the rear surface of the circuit board 382.

In an embodiment, motor 300 additionally includes a front bearingsupport structure (also referred to as front bearing bridge) 330, and arear bearing support structure (also referred to as rear bearing bridge)340 disposed on two ends of the motor can 302 to support front and rearbearings 304 and 306 of the rotor shaft 322 relative to the motor can302. Front and rear bearing bridges 330 and 340 include some of thefeatures and functions previously described with reference to front andrear bearing bridges 130 and 140. In an embodiment, front bearing bridge330 includes a main cylindrical body 332 forming a bearing pocket forsecurely receiving an outer race of a front bearing 304 mounted on therotor shaft 322. In an embodiment, rear bearing bridge 340 similarlyincludes a cylindrical body 342 forming a bearing pocket for securelyreceiving an outer race of a rear bearing 306 mounted near a rear end ofthe rotor shaft 322. In an embodiment, the sense magnet 307 ispositioned within the cylindrical body 342 of the rear bearing bridge340 with an airgap in between so it is not in physical contact with therear bearing bridge 340. In an embodiment, a significant portion of therear bearing bridge 340 is located inside the routing insulator 360 andincludes features for its piloting and support relative to the innersurface of the stator core 312. Improvements to front and rear bearingbridges 330 and 340 and features thereof are discussed in detail laterin this disclosure.

In an embodiment, front bearing bridge 330 is secured to the motor can302 via one or more fasteners 338 received radially from outside themotor can 302. In an embodiment, rear bearing bridge 340 is similarlysecured to the motor can 302 via one or more fasteners 352 receivedradially from outside the motor can 302. In an embodiment, one or moreretaining insert members 350 are provided to receive the ends of thefasteners 352. In an embodiment, the retaining insert members 350axially support the rear bearing bridge 340 relative to the statorassembly 310.

In an embodiment, the above-described arrangement provides for the rearbearing 306 being located between the circuit board 380 and the rotorassembly 310. In an embodiment, the rear bearing 306 is radially inwardof the routing insulator 340, and a radial plane that goes through therear bearing 306 intersects the routing insulator 340.

Referring particularly to FIG. 27, in an embodiment, motor 300 has anoverall total length M, as defined from a front end of the front bearingbridge 330 to a rear surface of the circuit board 382, of approximately65 mm to 110 mm, preferably approximately 67 mm to 105 mm, preferablysmaller than or equal to approximately 97 mm. The length of the statorcore 312 in this embodiment is approximately 30 mm to 47 mm, preferablyapproximately 34 mm to 42 mm, more preferably approximately 36 mm to 39mm, less than the total length M of the motor 300. In an embodiment,motor 300 also has a diameter DD, as defined by the outer diameter ofthe motor can 302, of approximately 32 mm to 38 mm, preferablyapproximately 34 mm to 36 mm, preferably no more than 35 mm. In anembodiment, the stator core 312 has a diameter that is approximately 2mm to 4 mm less than the diameter DD of the motor can 302. In anembodiment, there is approximately a 0.5 mm radial airgap between thestator core 312 and the inner surface of the motor can 302.

In an embodiment, a magnetic length MMAG of the motor 100 designates alength of the motor 300 in which magnetic components of the motor,including magnet wires and magnets, are located. In an embodiment,magnetic length MMAG is measured between frontmost and rearmost ends ofthe stator windings 514. This will be described later in detail.

These dimensions allow for motor 300 to fit into the small girth of thehousing of a power tool while producing enough power for variousoperating including, but not limited to, grinding, cutting, impacting,drilling, etc. In an embodiment, motor 300 is configured to producemaximum long duration power output of at least approximately 450 watts,preferably at least approximately 500 watts. In an embodiment, testsconducted on motor 300 have proved them capable of producing a maximumlong-duration power output (i.e., continuous power output at full motorspeed over one discharge cycle of the battery pack from full charge ofthe battery pack until the battery voltage reaches a cut-off threshold)of greater than or equal to approximately 500 watts for a 30 mm statorstack length, 700 watts for a 48 mm stator stack length, and 8-watts fora 60 mm stator stack length.

FIGS. 28 and 29 depict side perspective views of the stator assembly310, according to an embodiment. As discussed briefly above, front endinsulator 316 and rear end insulator 360 (also referred to as routinginsulator 360) are mounted on opposing axial ends of the stator core 312to insulator the stator windings 314 (not shown) from the stator core312.

In an embodiment, front end insulator 316 is shaped as an annular bodyand includes a series of inwardly-projecting teeth 317 that lay on frontends of the stator teeth 311 of the stator core 112. The front portionsof the stator windings 314 are electrically insulated from the statorcore 112 via the teeth 317 of the front end insulator 316. A series oftongues 313 project axially from the annular body into axial grooves 315formed longitudinally along the outer surface of the stator core 112 torotationally fix the front end insulator 316 to the stator core 112prior to winding of the stator windings 314. In an embodiment, thetongues 313 may be press-fit into the axial grooves 315 to furtherprovide axial retention for the front end insulator 316 relative to thestator core 112. In an embodiment, the front end of the front endinsulator 316 includes a series of bumps 319 projecting axially oppositethe stator core 312. In an embodiment, the front end insulator 316extends approximately 2 mm to 6 mm along the axial direction.

FIGS. 30 and 31 depict side perspective views of the routing insulator360, according to an embodiment. As shown here, and with continuedreference to FIGS. 28 and 29, routing insulator 360 includes an annularbody 365 and a series of inwardly-projecting teeth 361 that lay on rearends of the stator teeth 311 of the stator core 112. The rear portionsof the stator windings 314 are electrically insulated from the statorcore 112 via the teeth 361 of the routing insulator 360. A series ofpins 362 project axially from the annular body 365 into the axialgrooves 315 of the stator core 112 to rotationally align and fix therouting insulator 360 to the stator core 112. In an embodiment, the pins362 may be press-fit into the axial grooves 315 to provide axialretention for the routing insulator 360 relative to the stator core 112.In an embodiment, the annular body 365 of the routing insulator 360extends approximately 13 mm to 20 mm, preferably approximately 15 mm to18 mm, along the axial direction. In an embodiment, the annular body 365has a thickness of 3 mm or less.

In addition to providing electric insulation for the stator windings314, the routing insulator 360 includes several pairs of retainingmembers 364 and 366 projecting axially-rearwardly from its rear surfaceto support stator terminal 390 for connections of the respective statorwindings 314 to the circuit board assembly 380. Further, the routinginsulator 360 includes support posts 363 projecting from a subset of theretaining members 366 to support the mounting of the circuit boardassembly 380. Moreover, the routing insulator 360 includes peripheralopenings 368 and other features for piloting and supporting the rearbearing bridge 340. These features are disclosed here in detail.

It is initially noted that while the stator terminals 390 and itssupport mechanism on the routing insulator 360 is described hereinaccording to an exemplary embodiment, any of the previously-describedstator terminal and routing insulator mounting configurations previouslydescribed with reference to FIGS. 14-20 may be alternatively employed.

FIG. 32 depicts a partially exploded view of the rear end of the statorassembly 310, showing the stator terminals 390 prior to mounted to therouting insulator 360, according to an embodiment.

In an embodiment, each stator terminal 390 includes a main body having afirst portion 391 that is arcuate or planar shaped and a second portion392 that extends angularly-inwardly from the first portion 391 at a 10to 30 degree angle; a tang portion 394 that extends from a lower side ofthe second portion 392 (i.e., the side facing the stator core 312) andis folded over the second portion 392 at an angle of approximately 30 to60 degrees; and two axial legs 396 and 398 that extend respectively fromthe lower sides of main body. The two axial legs 396 and 398 include aribbed or teethed profile. Each retaining member 364 and 366 of therouting insulator 360 includes axial grooves therein sized to receivethe axial legs 396 and 398. As the stator terminals 390 are mounted onthe routing insulator 360, legs 396 and 398 of each stator terminal 390are slidingly received into the grooves of corresponding retainingmembers 364 and 366 of the routing insulator 360, with the ribbed sidesof the legs 396 and 398 making interference-fit connections to securelyretain the stator terminals 390 to the retaining members 364 and 366.

In an embodiment, stator terminals 390 include terminal pins 395projecting axially away from the routing insulator 360 opposite the legs398. In an embodiment, terminal pin 395 and leg 398 of each statorterminal 390 are disposed proximate a side edge of the first portion391, which is folded inwardly at an approximately 90 degree angle toensure that that terminal pin 395 and leg 398 are located radiallyinwardly of the first portion 391.

FIG. 33 depicts a partial view of the rear end of the stator assembly310, showing the stator terminals 390 and the stator windings 314 afterthe winding process, according to an embodiment. FIG. 34 depicts across-sectional angular view of the rear end of the stator 310 aftercompletion of the winding process and a fusing process, according to anembodiment.

In an embodiment, after routing insulator 360 and front end insulator316 are mounted on two ends of the stator core 312 and the statorterminals 390 are mounted on the routing insulator 360, stator windings314 are wound on the stator teeth 311 of the stator core 312. In thisstep, a magnet wire is wound on successive stator teeth 311 to form thestator winding 314, with cross-over portions 318 of the magnet wirepassing between the stator windings 314 in contact with the statorterminals 390. In an embodiment, the cross-over portions 318 extendaxially away from the stator windings 314 within the body of the routinginsulator 360 radially outward of main cylindrical body 342 of thebearing bridge 340. The cross-over portions 318 are guided out of therouting insulator 360 in contact with the outer surfaces of the mainbody of the stator terminals 390, and are captured in the foldedportions of the tang portions 394, before being routed back inside therouting insulator 360 for winding of the adjacent stator winding 314.After this process is complete, in an embodiment, the tang portions 394are pressed against the cross-over portions 318 of the magnet wire andthe cross-over portions 318 are fused to make electrical connectionswith the respective tang portions 394.

FIG. 35 depicts a rear axial view of the stator assembly 310 after thewinding process and fusing processes, according to an embodiment.

In an embodiment, the radially-inward angular orientation of the secondportion 392 relative to the first portion 391 of the main body of eachstator terminals 390 ensures that the tang portion 394, when pressedagainst the second portion 392, is not located radially outwardly of thefirst portion 391. As such, the stator terminals 390 can be located ator near the outer periphery of the routing insulator 360, without thetang portions 394 projecting radially outwardly outside thecircumferential envelope of the routing insulator 360. The arcuate orangular shapes of the main bodies allows them to be fully located withinthe circumferential envelope of the stator assembly 310. After the tangportions 394 are pressed in against the second portion 392, the statorterminals 390 become substantially and/or entirely located within thecircumferential envelope of the stator assembly 310 and thecircumferential envelope of the annular body 365 of the routinginsulator 360. In an embodiment, as described above, the annular body365 of the routing insulator 360 has a thickness of 3 mm or less, andthe first portion 391 is mounted fully on the routing insulator 360. Inan embodiment, the second portion 392 slightly projects radiallyinwardly relative to the routing insulator 360.

In an embodiment, as shown in these figures, the main body (includingfirst and second portions 391, 392) of each stator terminal 390 extendscircumferentially at an angular distance 0 of approximately 33 to 53degrees, preferably approximately 37 to 48 degrees, preferablyapproximately 40 to 45 degrees. In an embodiment, no part of the statorterminals 390 pass through gaps 369 that are formed in the routinginsulator 360 between the retaining members 364 and 366 and in axialalignment with centerlines of the stator slots between adjacent statorwindings 314. In an embodiment, in each stator terminal 390, theterminal pins 395 is disposed on one side of the gap 369, the firstportion 391 passes along or near the outer circumference of the mainannular body 354 radially outwardly of the gap 369, and the secondportion 392 and the tang portions 394 are disposed on the other side ofthe gap 369. This arrangement ensures that the stator terminals 390 donot interfere with the assembly of the rear bearing bridge 340 withinthe routing insulator 360, as described below.

After the winding and routing process of the magnet wire as describedabove is completed, according to an embodiment, the front and rearbearing bridges 330 and 340 are mounted to opposite ends of the statorassembly 310, with the rear bearing bridge 340 being positioned insidethe body of the routing insulator 360. The mounting process of the rearbearing bridge 340 is initially described here.

FIG. 36 depicts a partially exploded perspective view of the statorassembly 310 and the rear bearing bridge 340, according to anembodiment. FIG. 37 depicts a perspective view of the rear bearingbridge 340 mounted inside the body of the routing insulator 360,according to an embodiment. FIG. 38 depicts an angular cross-sectionalview of the rear bearing bridge 340 mounted inside the body of therouting insulator 360, according to an embodiment. FIG. 39 depicts aradial cross-sectional view of the rear bearing bridge 340 mountedinside the body of the routing insulator 360 along a plane A-A,according to an embodiment.

In an embodiment, as shown in these figures, and with continuedreference to FIGS. 25-27 and 35, rear bearing bridge 340, in addition tomain cylindrical body 342 for retention of the rear bearing 306,includes a series of axial post inserts 344 projecting radiallyoutwardly from the outer circumference of the main cylindrical body 342and extending in the axially forward direction in the direction of thestator core 312. The outer circumference of the cylindrical body 342 issized to be slidingly received in contact with the inner body of therouting insulator 360. The axial post inserts 344 are sized to bereceived within gaps 369 (FIG. 35) of the routing insulator 360 to comeinto contact with the stator core 312, as detailed below.

In an embodiment, as the rear bearing bridge 340 is slidingly receivedwithin the routing insulator 360, the outer surface of the cylindricalbody 342 comes into sliding contact with the inner surfaces of theretaining members 364 and 366 of the routing insulator 360 and becomesstructurally supported by these features. In an embodiment, firstportions 344 a of the axial post inserts 344 that are located around thecylindrical body 342 are received into gaps 369 of the end insulator 360and come into contact with the inner surface of the annular body 365 ofthe routing insulator 360. In an embodiment, second portions 344 b ofthe axial post inserts 344 that extend axially forward from thecylindrical body 342, having already passed through the gaps 369, areslidingly received into the stator slots between adjacent statorwindings 314 and are form-fittingly pressed into the inner body of thestator core 312. Engagement of the axial post inserts 344 with thestator core 312 pilots and radially supports the rear bearing bridge340, and thus the rear bearing 306, relative to the stator assembly 310.In an embodiment, friction force between the post inserts 344 and thestator core 312 further rotationally secures the rear bearing bridge340. In an embodiment, the post inserts 344 and the stator core 312 maybe provided with snapping or tongue-and-groove retention features to fixthe post inserts 344 more robustly along the rotational direction.

In some power tool applications with relative low torque ratings, thepiloting of the rear bearing bridge 340 relative to the stator assembly310 via the post inserts 344 is sufficient to provide full structuralsupport for the rear bearing bridge 340. However, in higher torque powertool applications, the support provided merely by this structure may beinsufficient.

In an embodiment, rear bearing bridge 340 further includes one or morenotches 346 formed through the outer edged of the first portions 344 aof the axial post inserts 344. After the rear bearing bridge 340 isfully received within the routing insulator 360, the notches 346 areradially aligned with peripheral openings 368 of the routing insulator360. Notches 346 are provided for insertion of retaining insert members350 or similar retention features from an outer tool housing for radialretention of the rear bearing bridge 340. This allows the tool housingto provide additional structural support for the rear bearing bridge340, as discussed in detail herein.

FIG. 40 depicts a partial perspective view of the stator assembly 310after the rear bearing bridge 340 is mounted inside the body of therouting insulator 360 but prior to assembly of the retaining insertmembers 350, according to an embodiment. FIG. 41 depicts a partialzoomed-in view of the stator assembly 310 showing one retaining insertmember 350 received within a corresponding peripheral opening 368 of therouting insulator 360, according to an embodiment. FIG. 42 depicts apartial zoomed-in view of the stator assembly 310 cross-sectioned alonga radial plane, according to an embodiment. FIG. 43 depicts across-sectional perspective view similar to FIG. 38, additionallyprovided with retaining insert members 350, according to an embodiment.

In an embodiment, retaining insert members 350 are received radiallyinto peripheral openings 368 of the routing insulator 360 to engage thenotches 346 of the axial post inserts 344. Each retaining insert member350 includes an outer surface 358 having approximately the same area asthe peripheral openings 368 that is rounded so as to be substantiallyflush with the outer body of the routing insulator 360 after theretaining insert member 350 is fully inserted so as to engage the innersurface of the motor can 302. Each retaining insert member 350 furtherincludes a penetrating portion 356 that penetrates radially through andis shaped for engagement with a corresponding notch 346 of the rearbearing bridge 340. In their fully inserted position, the retaininginsert members 350 axially and/or radially lock the rear bearing bridge340 relative to the routing insulator 360.

In an embodiment, each retaining insert member 350 further includes afastening receptacle 354 extending through the outer surface 358 along aradial direction of the motor 300. In an embodiment, fasteners 352(FIGS. 25 and 27) are fastened into the fastening receptacles 352 tosecure the rear bearing bridge 340 to the motor can 302 and/or otherhousing structures.

Alternatively, in an embodiment, at least a subset of the retaininginsert members 350 may be include no fastening receptacles and beprovided for radial piloting and support of the rear bearing bridge 340and/or the routing insulator 360 to the motor can 302 and/or otherhousing structures.

In an alternative and/or further embodiment, at least a subset of theretaining insert members 350 may be made of resilient deformablematerial such as silicone or rubber, with the outer surfaces 358projecting slightly outwardly relative to the annular body 365 of therouting insulator 360. In this embodiment, as the routing insulator 360is received within the motor can 302, the retaining insert members 350compress inwardly against the surface of the motor can 302, thusabsorbing any radial stack-up tolerances and improving radial pilotingand support of the rear bearing bridge 340 and/or the routing insulator360 relative to the motor can 302.

FIG. 44 depicts a perspective view of the circuit board assembly 380prior to mounting onto the stator assembly 310, according to anembodiment. FIG. 45 depicts a perspective view of the circuit boardassembly 380 mounted onto the stator assembly 310, according to anembodiment.

As previously described, circuit board assembly 380 includes circuitboard 382 mounted on the rear end of the rear bearing bridge 340. Thecircuit board 382 includes a series of magnetic sensors (not shown)mounted on its front surface (in this figure, bottom surface) inmagnetic interface with the sense magnet 307 of the stator assembly 310.The circuit board 382 includes an outer periphery that includesapproximately the same diameter as the cylindrical body 342 of the rearbearing bridge 340. Further, the diameter of the outer circumference ofthe main body of the circuit board 382 is smaller than a circumferenceof an envelope formed by the stator terminals 390. The circuit board 382further includes a series of fingers 386 a and 386 b projecting radiallyoutwardly from its outer periphery and forming peripheral slots 386therein. Peripheral slots 386 are positioned to receive the statorterminals 390 from the stator assembly 310. In an alternativeembodiment, peripheral slots 386 may be holes formed close to the outerperiphery of the circuit board 382. Peripheral slots 386 align with andreceive terminal pins 395 of the stator terminals 390 securely therein.Conductive traces within the circuit board 382 extends into theperipheral slots 386 to make electrical connections with the terminalpins 395 of the stator terminals 390. This allows the circuit board 382to provide appropriate interconnections between the stator windings 314of different phases.

In an embodiment, circuit board 382 additionally includes one or morethrough-holes 383 provided adjacent at least a subset of the peripheralslot 386 in alignment with support posts 363 of the routing insulator360. As the circuit board assembly 380 is mounted on the stator assembly310, the support posts 363 are securely received within thethrough-holes 383 to spatially support the circuit board assembly 380relative to the routing insulator 360 and, by extension, the statorassembly 310.

In an embodiment, power wires 389 and signal wires 388 are secured to arear (top) surface of circuit board assembly 380. In an embodiment,overmold structure 381 is formed around at least the rear surface of thecircuit board 382, forming a continuous wall around the mounting pointsof the power wires 389 and signal wires 388. In an embodiment, overmoldstructure 381 is further provided on the front surface of the circuitboard 382, forming an annular body for providing a sealed mating surfacewith the cylindrical body 342 of the rear bearing bridge 340.

FIG. 46 depicts a partially exploded perspective view of the circuitboard assembly 380 relative to the rear bearing bridge 340, according toan embodiment. As shown here, the annular body formed by the overmoldstructure 381 on the front surface of the circuit board 382 includesapproximately the same diameter as the cylindrical body 342 of the rearbearing bridge 340. In an embodiment, the annular body of the overmoldstructure 381 includes an annular groove 385 on its front surface, whichreceives an annular lip 341 of the cylindrical body 342 of the rearbearing bridge 340. This allows the circuit board assembly 380 tosubstantially seal off the hollow opening of the cylindrical body 342 ofthe rear bearing bridge 340, thus protecting the rear bearing 306, thesense magnet 307, and the magnetic (Hall) sensors (not shown), fromingress of dust and debris particles.

FIG. 47 depicts a perspective view of the circuit board assembly 380mounted onto the stator assembly 310, according to an embodiment. Thisfigure provides a similar view as FIG. 45, but further highlights aseries of air inlets 387 formed between the circuit board 382, therouting insulator 360, and the stator terminals 390. The airflowgenerated by the motor fan 308 enters the motor assembly 300 through airinlets 387, in thermal contact with the circuit board assembly 380, andthrough the stator assembly 310. In an embodiment, the air inlets 387include radial portions and circumferential portions. In an embodiment,the outer circumferential surface of the circuit board 382 is recessedbetween adjacent peripheral slots 386 and forms the radial portions ofthe air inlets 387. In an embodiment, gaps formed between adjacentstator terminals 390 and between the stator terminals 390 and therouting insulator 360 form the circumferential portions of the airinlets 387.

FIG. 48 depicts a partial perspective view of the stator assembly 310being received through an end of the motor can 302, according to anembodiment. FIG. 49 depicts a partial perspective view of the motor can302 with the stator assembly 310 fully inserted therein, according to anembodiment.

As shown in these figures, in an embodiment, motor can 302 includes oneor more side openings 370. As the stator assembly 310 is being receivedthrough the rear open end of the motor can 302, the side openings 370are axially aligned with fastening receptacles 354 of the retaininginsert members 350. Once the stator assembly 310 is properly positionedwithin the motor can 302, fasteners 352 are received radially throughthe side openings 370 into the fastening receptacles 354 to secure themotor can 302 to the rear bearing bridge 340 and the stator assembly310.

In an embodiment, after the stator assembly 310 is mounted into themotor can 302, the rotor assembly 320 is received through the front openend of the motor can 302 and the front bearing bridge 330 is secured tothe front open end of the motor can 302, as described herein in detail.

FIGS. 50 and 51 depict partial exploded perspective views of the rotorassembly 320 and the front bearing bridge 330 prior to mounting into themotor can 302 and the stator assembly 310, according to an embodiment.

In an embodiment, referring to these figures and FIG. 27, front and rearbearings 304 and 306 are mounted on the rotor shaft 322 on oppositesides of the series of permanent magnets 326. Sense magnet 307 is alsomounted of the rotor shaft 322 rearward of the rear bearing 306. In anembodiment, the front bearing 304 is nested within the bearing pocketformed by the main cylindrical body 332 of the front bearing bridge 330prior to insertion of the rotor assembly 320 into the motor can 302.During the mounting process, the rear bearing 306 is guided into thecylindrical body 342 of the rear bearing bridge 340. Once the frontbearing bridge 330 is secured to the motor can 302, the rotor assembly310 has full axial and radial structural support relative to the statorassembly 310.

In an embodiment, in addition to main cylindrical body 332 for receivingthe front bearing 304, the front bearing bridge 330 further includes aseries of radial arms 334 that project outwardly from the maincylindrical body 332, and an outer ring 336 configured to mate with thefront end of the motor can 302. In an embodiment, outer ring 336 isfittingly received inside the inner surface of the motor can 302 toradially pilot and structurally support the front bearing bridge 330,and therefore the front bearing 304, relative to the motor can 302. Inan embodiment, an annular lip 337 radially projects outwardly from theouter ring 336 to mate with the end surface of the motor can 302. In anembodiment, the outer ring 336 further includes a series of fasteningreceptacles 339 facing radially outwardly, and the motor can 302includes a series of corresponding side openings 372 through whichfasteners 338 (FIG. 27) are received radially into the fasteningreceptacles 339 to secure the motor can 302 to the front bearing bridge330.

In an embodiment, motor fan 308 is disposed adjacent the front bearingbridge 330. The airflow generated by the motor fan 308 passes throughthe openings formed between the radial arms 334 of the front bearingbridge 330 towards the motor fan 308. In an embodiment, the frontbearing bridge 330 forms a baffle for the air to be repelled along theradial direction away from the motor fan 308. In an embodiment, the sizeof the fan 308 may be configured according to motor power outputrequirements. In the illustrated embodiment, the fan 308 includesapproximately the same diameter as the motor can 302.

In an embodiment, in its mounted position, the front bearing bridge 330axially restrains the front end of the stator assembly 310 within themotor can 302. To absorb stack-up tolerances resulting frommanufacturing inaccuracies in, for example, the length of the statorassembly 310, length of the motor can 302, placement of the sideopenings 370 and 372, or placement of the fastening receptacles 354 and339, a compression ring 374 is provided inside the motor can 302 betweenthe front end of the front end insulator 316 and the rear end of thefront bearing bridge 330.

FIG. 52 depicts a partially exploded view of the front end of the motorcan 302 and the front bearing bridge 330, according to an embodiment.FIGS. 53 and 54 depict zoomed-in cross-sectional views of the front endof the motor can 302, according to an embodiment.

As shown in these figures, in an embodiment, the compression ring 374includes a length of, for example, at least approximately 1 mm along theaxial direction. The compression ring 374 may include an outer diameterthat is approximately equal to or slightly smaller than the innerdiameter of the motor can 302, allowing it to be sandwiched between thebetween the front end of the front end insulator 316 and the rear end ofthe front bearing bridge 330 inside the motor can 302. Alternatively,the outer diameter of the compression ring 374 may be slightly greaterthan the inner diameter of the motor can 302 for added radial dampening.As the front bearing bridge 330 is initially mounted on the front end ofthe motor can 302 and prior to the fasteners 338 being fastened, theaxial width of the compression ring 374 causes the side openings 372 tobe slightly axially misaligned relative to the fastening receptacles339. Fastening the fasteners 338 through the side openings 372 into thefastening receptacles 339 causes the front bearing bridge 330 to move inthe direction F towards the stator assembly 310 against the biasingforce of the compression ring 374, thus compressing the compression ring374 between the front end of the front end insulator 316 and the rearend of the front bearing bridge 330. This ensures that the compressionring 374 absorbs all stack-up tolerances, and consequently reducevibration and noise, while firmly supporting the stator assembly 310relative to the front bearing bridge 330 along the axial direction.

In an embodiment, the front bearing bridge 330 includes rounded areas333 formed rearward of the fastening receptacles 339, and thecompression ring 374 includes corresponding rounded recesses 376. As thefasteners 338 are tightened into fastening receptacles 339, the roundedareas 333 press against the rounded recesses 376 in the direction F,thus compressing the compression ring 374 against the front end of thefront end insulator 316.

FIG. 55 depicts a partial perspective view of the motor can 302 with thecompression ring 374 at a distance from the front end of the front endinsulator 316, according to an embodiment. FIG. 56 depicts a partialperspective view of the motor can 302 with the compression ring 374received in contact with the front end insulator 316, according to anembodiment.

As shown in these figures, in an embodiment, a rear surface of thecompression ring 374 that is arranged to come into contact with thefront end of the front end insulator 316 includes contoured profileincluding a series of humped surfaces 378 designed to fit into recessesformed between bumps 319 of the front end insulator 316.

Embodiments described above are made with reference to a canned BLDCmotor having a motor can 302 in which the motor components including thestator assembly 310 are received and to ends of which the front and rearbearing bridges 330 and 340 are secured. The motor can 302, in anembodiment, may be a solid cylindrical metal piece having two open ends.

An alternative embodiment of the invention, described here in detail,utilizes the same motor components described above directly in aclamshell housing 402 without an intermediary motor can 302.

FIG. 57 depicts a perspective view of a clamshell housing 402 forhousing the motor 300, according to an embodiment. FIGS. 58 and 59depict two partially exploded views of the clamshell housing 402relative to the motor 300, according to an embodiment. FIG. 60 depictsan exploded view of the motor 300 components and the clamshell housing402, according to an embodiment.

In an embodiment, components of the motor 300 remain unchanged exceptthat it includes an alternative front bearing bridge 430 configuration.In this embodiment, front bearing bridge 430 includes substantially thesame features as front bearing bridge 330 described above, but it doesnot include fastening receptacles along the sides of its outer ring forreceiving fasteners. Rather, the front bearing bridge 430 includes aseries of axial post inserts 432 arranged to be securely received intostator slots of the stator assembly 310 for piloting and supporting thefront bearing bridge 430 directly to the stator assembly 310. Thisensures that the front bearing bridge 430, like the rear bearing bridge340, is structurally secured to the stator assembly 310 independently ofan exterior motor can.

In an embodiment, the clamshell housing 402 includes two clamshells 402a and 402 b that come together around the stator assembly 310 to supportthe motor 300. Clamshell housing 402 may be provided as a substitute formotor can 302 described above. Alternatively, clamshell housing 402 maybe a part of a tool housing that receives the motor. In an embodiment,clamshell housing 402 may correspond to, or be a part of, the elongatehousing 12 of the power tool 10 previously described with reference toFIG. 1, or the elongate housing 52 of power tool 50 later described withreference to FIGS. 66-68. As such, clamshell housing 402 may beconstructed from molded plastic material, though it should be understoodthat the clamshell housing 402 may be made, in part or fully, of metal.This arrangement allows the elongate housings 12 and 52 to support themotor 300 components directly without utilizing an intermediary motorcan 302. This arrangement reduces the overall girth of the elongatehousings 12 and 52. Clamshell housing 402 is illustrated here by way ofexample as having a length corresponding to the length of the motor 300,though it should be understood that clamshell housing 402 may havedifferent shapes or sizes in accordance with shape or size requirementsof the power tool.

In an embodiment, clamshell 402 a and 402 b are arranged to be fastenedtogether around the stator assembly 310, with the inner surfaces of theclamshell assembly 402 being formed around the stator core 312. In anembodiment, the clamshell assembly 402 comes into surface contact withat least a portion of the outer surface of the stator core 312. In anembodiment, an airgap may be maintained between the clamshell assembly402 and the outer surface of the stator core 312. In an embodiment, aseries of supporting pads may be disposed on the inner surfaces of theclamshell assembly 402 to insulate the stator core 312 from theclamshell assembly 402.

In an embodiment, clamshell housing 402 includes a first set of ribs 404provided on the inner surfaces of the clamshell 402 a and 402 b, eachrib extending along the axial direction for a distance that is smallerthan the length of the stator core 312. In an embodiment, the first setof ribs 404 includes one or more rows of ribs 404 provided on the innersurface of each clamshell 402 a and 402 b. The first set of ribs 404 arereceived into the axial grooves 315 of the stator core 312 when theclamshell housing 402 is fully assembled around the stator assembly 310,thus rotationally fixing the stator assembly 310 to the clamshellassembly 402. In a further embodiment, the first set of ribs 404 may beshaped and configured to apply a tight press against the axial grooves315 to further provide radial support for the stator assembly 310.

FIGS. 61 and 62 depict partially exploded views of the front end of theclamshell housing 402 and the motor 300, according to an embodiment. Inan embodiment, as shown here and with continued reference to FIG. 58,clamshell housing 402 includes a second set of ribs 406 projecting fromthe inner surfaces of the clamshell 402 a and 402 b, and extending alongthe circumferential direction intersecting a first radial plane radiallyaligned with the front end insulator 316. In an embodiment, front endinsulator 316 includes a series of first exterior pockets 410 formed asrecesses it its outer surface in cooperation with the front end of thestator core 312. The second set of ribs 406 are configured and orientedto be fittingly received into the first exterior pockets 410 to axiallyretain and support the front end insulator 316 relative to the clamshellhousing 402. In a further embodiment, where the first set of ribs 404merely provides rotational support for the stator core 312, the secondset of ribs 406 may be shaped and configured to tightly engage the firstexterior pockets 410 to additionally provide radial and rotationalsupport for the stator assembly 310.

In an embodiment, with continued reference to FIGS. 58, 61 and 62,clamshell housing 402 further includes a third set of ribs 408projecting from the inner surfaces of the clamshell 402 a and 402 b, andextending along the circumferential direction intersecting a secondradial plane that is radially forward of the first radial plane and isradially aligned with the front bearing bridge 430. In this example, thethird set of ribs 408 are oriented near the front edge of the clamshellhousing 402. In an embodiment, front bearing bridge 430 includes aseries of second exterior pockets 412 formed as recesses it its outersurface and facing the fan 308. The third set of ribs 408 are configuredand oriented to be fittingly received into the second exterior pockets412 to axially retain and support the front bearing bridge 430 relativeto the clamshell housing 402. In a further embodiment, where the firstset of ribs 404 merely provides rotational support for the stator core312, the third set of ribs 408 may be shaped and configured to tightlyengage the second exterior pockets 412 to additionally provide radialand rotational support for the stator assembly 310. In an embodiment,this may be in cooperation with the second set of ribs 406 radially androtationally retaining the front end insulator 316.

FIGS. 63 and 64 partially exploded views of the rear end of theclamshell housing 402 and the motor 300, according to an embodiment. Inan embodiment, as shown here and with continued reference to FIG. 59,clamshell housing 402 includes a fourth set of ribs 414 and 416projecting from the inner surfaces of the clamshell 402 a and 402 b andintersecting a third radial plane that is radially aligned with theperipheral openings 368 of the routing insulator 360. In an embodiment,ribs 416, at least one of which is provided on each clamshell 402 a and402 b, are retaining members that project radially inwardly through theperipheral openings 368 to engage with and provide axial and radialsupport for the rear bearing bridge 340, as described below.Furthermore, in an embodiment, ribs 414 and outer portions of ribs 416are configured and oriented to be fittingly received into the peripheralopenings 368 to provide axial support for the routing insulator 360relative to the clamshell housing 402. In a further embodiment, wherethe first set of ribs 404 merely provides rotational support for thestator core 312, the fourth set of ribs 414 and 416 may be shaped andconfigured to tightly engage the peripheral openings 368 to additionallyprovide radial and rotational support for the stator assembly 310. In anembodiment, this may be in cooperation with the second and third sets ofribs 406 and/or 408 radially and rotationally retaining the front endinsulator 316 and/or the front bearing bridge 430 respectively.

FIG. 65 depicts a partially exploded side cross-sectional view of therear end of the clamshell housing 402 and the motor 300, according to anembodiment. In an embodiment, the ribs 416 project radially inwardlythrough the peripheral openings 368 of the routing insulator 360 andtheir inner tips are fittingly received into corresponding notches 346of the axial post inserts 344 of the rear bearing bridge 340. In anembodiment, where only two opposing ones of the axial posts inserts 344include notches 346, ribs 416 are disposed opposite one another onclamshell 402 a and 402 b. It should be understood, however, that threeor more of the axial post inserts may include notches 346, and thecorresponding number or rib 416 may accordingly be provided. Engagementof the inner tips of the ribs 416 with notches 346 allows the clamshellhousing 402 to structurally support and retain the rear bearing bridge340 along the radial and axial directions, even though the routinginsulator 360 circumferentially surrounds the rear bearing bridge 340and is located between the clamshell housing 402 and the rear bearingbridge 340.

In an alternative and/or further embodiment, at least a subset of theretaining insert members 350 may be made of resilient deformablematerial such as silicone or rubber, with the outer surfaces 358projecting slightly outwardly relative to the annular body 365 of therouting insulator 360. In this embodiment, as the routing insulator 360is received within the motor can 302, the retaining insert members 350compress inwardly against the surface of the motor can 302, thusabsorbing any radial stack-up tolerances and improving radial pilotingand support of the rear bearing bridge 340 and/or the routing insulator360 relative to the motor can 302.

Another exemplary power tool 50 including a BLDC motor 500 is describedherein, according to an embodiment.

FIG. 66 depicts a perspective view of power tool 50. FIG. 67 depicts across-sectional view of the power tool 50, according to an embodiment.FIG. 68 depicts a top view of the power tool 50, according to anembodiment.

Referring to these figures, in an embodiment, power tool 50 includeselongate housing 52 made of two clamshells, with one clamshell removedin this figure to expose the internal components of the power tool 50including the motor 500, according to an embodiment. Power tool 50,which is in this example is a grinder, includes many of the samefeatures as power tool 10 described above. Among other features, powertool 50 includes a gear case 54 mounted forward of the housing 52, abattery receptacle 56 formed rear of housing 52, a trigger assembly 60,etc. In an embodiment, motor 500 is substantially similar to motor 300described above, with key differences described later in thisdisclosure. In comparison to motor 100 of the first embodiment, motor500 includes a smaller overall length.

In an embodiment, battery receptacle 56 is configured to receive aremovable and rechargeable power tool battery pack therein. The batterypack, not shown in this figure, may be, for example a lithium-ionbattery pack having a nominal voltage of 18V. In this embodiment, thereceiving axis of the battery pack is parallel to the longitudinal axisof the elongate housing 52. In an embodiment, battery receptacle 56includes a battery terminal block 58 oriented below the envelope of theelongate housing 52 adjacent the trigger assembly 60.

In an embodiment, trigger assembly 60 is mounted on the housing 52adjacent the terminal block 58. In an embodiment, the trigger assembly60 includes a paddle switch 62 engageable by a user and a plunger 64moveable with the paddle switch 62 into the housing 52. In anembodiment, the paddle switch is pivotable relative to the housing 52 ata pivot point 66 that is adjacent to and axially in-line with theterminal block 58. In an embodiment, paddle switch 62 includes aspring-loaded lock 67 that is engageable by the user on one end and isin sliding contact with a rib 65 of the housing 52 on another end.

In addition, in an embodiment, power tool 50 includes a control module70, which in this example is disposed within the housing 52 extendingfrom the rear of the motor 500 to above the terminal block 58. In anembodiment, control module 70 includes a programmable controller, suchas a microcontroller device, not shown in this figure, mounted on aprinted circuit board. The controller includes code that controls supplyof electric power to the motor 500 according to various criteria, suchas load, speed, and power requirements. In an embodiment, control module70 may further include a series of power switches, also not shown,configured as a three-phase inverter circuit, controlled by thecontroller for driving the motor 500. One or more heat sinks may be alsobe provided to dissipate heat away from the power switches and othercomponents. The controller and the power switches may be mounted on asignal printed circuit board, or on two or more printed circuit boards.Furthermore, in an embodiment, the control module 70 may integrallyinclude an input unit including components that interface with theplunger 64 for ON/OFF and variable-speed control. U.S. Pat. Nos.9,508,498; 10,541,588; 10,497,524; and US Patent Publication No.2020/000,8300, all of which are incorporated herein by reference intheir entireties, provide various examples of control modules withintegrated power components and integrated input units that may beutilized.

In an embodiment, control module 70 may be constructed according to theteachings of U.S. application Ser. No. 17/587,003 filed Jan. 28, 2022,which is also incorporated herein by reference, to reduce the overallgirth required by the power module 70, allowing at least a front part ofthe control module 70 to fit within a greppable area of the elongatehousing 52. In an embodiment, the output terminals of the control module70 project out of a front wall of the housing rather than a top surfaceof the circuit board, providing for a more compact and robust designsuitable for a smaller diameter power tool.

In an embodiment, the power tool 50 is an angle grinder by way ofexample, though it should be understood that the principles describedherein may be utilized in various other power tools such as a cutouttool, a polisher, a wrench, a drill, an impact driver, a hammer drill, acircular saw, a reciprocating saw, a band saw, a nailer, etc.

In an embodiment, the gear case 54 receives a rotor shaft 522 that isrotatable with the motor 500. The gear case 54 supports an outputspindle 72 driven by the rotor shaft 422. In an embodiment, the outputspindle 72 may be oriented perpendicularly to the rotor shaft 322 andengage a pinion 88 mounted at the end of the rotor shaft 522 via one ormore gears 74. In an embodiment, the gear case 54 further includesstructural support for a pinion bearing 90 disposed near the end of theshaft 522 to support the pinion 88.

In an embodiment, the gear case 54 may additionally include a spindlelock 76 engageable by a user to prevent rotation of the rotor shaft 422or the output spindle 72 while the user is mounting a grinding orcutting wheel onto the output spindle. In an embodiment, the gear case54 may also include a retention flange 78 configured to apply a biasingforce to the grinding or cutting wheel for increased security, asdescribed in U.S. patent application Ser. No. 17/412,448 filed on Aug.26, 2021, which is incorporated herein by reference in its entirety. Inan embodiment a guard 80 may be mounted on a collar portion 81 of thegear case 54 around the grinding or cutting accessory.

In an embodiment, a front end 82 of the elongate housing 52 includes alarger diameter than the rest of the elongate housing 52 and isconfigured to mate with the gear case 54. In an embodiment, front end 82houses a motor adaptor 84 that is configured to similarly mate with thegear case 54, thus structurally securing the motor 500 to the end of thegear case 54. Motor adaptor 84 includes a recessed inner region arrangedto receive a motor fan 508 coupled to the motor 500. In an embodiment,front end 82 of the housing 52 and the motor adaptor 84 cooperativelyform one or more air exhaust openings 86 around the fan 508. Further, asthe fan 508 generates an airflow through the motor 500 along the axialdirection, the motor adaptor 84 forms a baffle to expel the airflowradially through the exhaust openings 86.

In an embodiment, the power tool 50 is designed as a body-grip powertool with the housing 52 being sized to fit into a hand grip of a userwith relative ease in the area around the motor 500. As such, in anembodiment, the housing 52 has a maximum diameter E of approximately 35to 45 mm, preferably approximately 37 to 44 mm, more preferably at most42 mm, and thus a circumference of at most 138 mm, preferably at mostapproximately 132 mm, around most of the length of the motor 500. In anembodiment, this maximum diameter E extends along length J of thehousing 52 (not including the rib 65 provided below the housing 52) whenviewed from the side of the tool 50. Length J of the housing 52, asmeasured from the frontal end 82 to a location between the motor 500 andthe control module 70, is approximately 60 mm to 110 mm, preferablyapproximately 80 mm to 100 mm, preferably at least approximately 90 mm.

In an embodiment, when viewed from the top of the tool 50, as shown inFIG. 68, the maximum diameter E extends along length J′ of the housing52, encompassing most of the length of the motor 500 (at leastsubstantially the steel laminations portions of the motor 500) as wellas a significant part of the control module 70. In an embodiment, lengthJ′ of the housing is approximately 150 mm to 210 mm, preferablyapproximately 160 mm to 200 mm, preferably approximately 170 mm to 190mm.

In an embodiment, referring back to FIG. 67, the housing 52 has a widthF of approximately 38 to 47 mm, preferably approximately 40 to 45 mm,more preferably at most 44 mm, around significant portion of the controlmodule 70. At a rear of the housing 52, including the battery receptacle56, the housing 52 has a width G of approximately 54 to 68 mm,preferably approximately 56 to 64 mm, more preferably at most 60 mm.

In an embodiment, the total length K of the housing 52, as measured fromthe front end 82 to the very end of the battery receptacle 56, isapproximately 220 mm to 280 mm, preferably approximately 230 mm to 270mm, more preferably approximately 240 mm to 260 mm. In an embodiment,the total length L of the power tool 50, as measured from the front ofthe gear case 54 to the very end of the battery receptacle 56, isapproximately 320 mm to 380 mm, preferably approximately 330 mm to 370mm, more preferably approximately 340 mm to 360 mm.

In an embodiment, the grip portion of the power tool 50, as defined bylength J′ of the housing having a diameter E as defined above, is atleast 40%, preferably at least 44%, preferably at least 48%, of thetotal length L of the power tool.

It should be understood that in power tool examples where the batteryreceptacle has a perpendicular or angular orientation, the ratio of thegrip portion J′ of the power tool 50 to its total length L may begreater than or equal to approximately 50%, preferably greater than orequal to approximately 55%, preferably greater than or equal toapproximately 57%.

As stated, motor 500 includes the main construction principles describedabove with reference to motor 300. While motor 300 represents a genericversion of the construction, motor 500 is customized for use with apower tool having an elongated housing, such as an angle grinder.Details of motor 500 are described herein with particular focus ondifferences between motors 500 and 300. To the extent that the twomotors share the same features, the same reference numerals areutilized.

FIG. 69 depicts a perspective view of the BLDC motor 500, according toan embodiment. FIG. 70 depicts a side cross-sectional view of the BLDCmotor 500, according to an embodiment. FIG. 71 depicts a perspectivecross-sectional view of the BLDC motor 500, according to an embodiment.

According to an embodiment, motor 500 includes a motor can 502 having asubstantially cylindrical body. Motor 500 further includes a statorassembly 510 having a stator core 512, stator windings 514, and a frontend insulator 516, as described above. These features are substantiallyas described above are therefore not described here further. In anembodiment, other features and components of the motor 500, includingthe rotor assembly 520, rotor shaft 522, front bearing bridge 530 forsupporting a front bearing 504 of the rotor shaft 522, rear bearingbridge 540 for supporting a rear rotor bearing 506 of the rotor shaft522, routing insulator 560, and circuit board assembly 580, includemodifications and/or improvements and are described below in detail asalternative embodiments.

FIG. 72 depicts a perspective view of the rotor assembly 520, accordingto an embodiment. As shown here, and with continued reference to FIGS.69-71, in an embodiment, rotor shaft 522 includes a stepped non-uniformconstruction. In this embodiment, the diameter of the rotor shaft 522varies from a rear end thereof, where the diameter RD of the rotor shaft522 is sized to be received within the inner race of the rear bearing504 and a sense magnet ring 507, to a core portion 525, where thediameter CD of the rotor shaft 522 increases to approximately greaterthan or equal to double the diameter RD. In an embodiment, permanentmagnet rings 526 are mounted directly on the core portion 525 of therotor shaft 522, thus eliminating the need for an intermediary rotorcore (e.g., rotor core segments 324 in the previous embodiment) disposedbetween the rotor shaft 522 and the permanent magnet rings 526. Thisarrangement also reduces the overall diameter of the rotor assembly. Inan embodiment, each permanent magnet ring 526 may be secured to the coreportion 525 of the rotor shaft 522 via adhesive and end alignmentmembers as previously described.

In an embodiment, the diameter of the rotor shaft 322 may be maintainedat approximate equal to or slightly smaller than CD at the mountinglocation of front bearing 504. In an embodiment, the front bearing 504has a larger outer diameter than the rear bearing 506 and the permanentmagnet rings 526.

In an embodiment, the diameter of the rotor shaft 522 decreasesgradually and/or in a step-wise fashion forward of the front bearing 504along the mounting location of the fan 508, the mounting location of thepinion bearing 90, and the mounting location of the pinion 88.

FIG. 73 depicts a partial exploded view of the front end of the motorcan 502 and the motor adaptor 84, according to an embodiment. As shownhere, and with continued reference to FIGS. 69-71, in an embodiment,front bearing bridge 530 includes many of the same features as frontbearing bridge 330 previously described. These features include a maincylindrical body 532 forming a bearing pocket for securely receiving anouter race of the front bearing 504, and an outer ring 534 that isfittingly received inside the front end of the motor cap 502 to radiallypilot and structurally support the front bearing bridge 530. In anembodiment, the outer ring 534 further includes a series of fasteningreceptacles 539 facing radially outwardly, and the motor can 502includes a series of corresponding side openings 572 through whichfasteners 538 are received radially into the fastening receptacles 539to secure the motor can 502 to the front bearing bridge 530. In anembodiment, a compression ring 574 is disposed inside the motor can 502between the front end of the front end insulator 516 and the rear end ofthe front bearing bridge 530 to absorb stack-up tolerances, aspreviously described.

In an embodiment, unlike the previously-discussed front bearing bridge330, which is provided as a discrete component, front bearing bridge 530is formed integrally with the motor adaptor 84 as a single component. Inan embodiment, a base portion 87 of the motor adaptor 84 is integrallycoupled to the outer ring 534 of the front bearing bridge 530, with theexhaust openings 86 formed forward of the front bearing bridge 530. Thisarrangement is particularly suitable for use in a power tool having alongitudinal body and a gear case, such as a grinder, providing astructure that secures and supports the front bearing bridge 530 to boththe gear case 54 of the power tool 50 and to the motor can 502.

FIG. 74 depicts a partial exploded view of the rear end of statorassembly 510 including the rear bearing bridge 540, according to anembodiment. FIG. 75 depicts a perspective view of the rear end of therear bearing bridge 540 mounted onto the stator assembly 510, accordingto an embodiment. FIG. 76 depicts a zoomed-in cross-sectional view ofthe rear end of the motor assembly 500, according to an embodiment. Therouting insulator 560, rear bearing bridge 540, and circuit boardassembly 580 are described herein with reference to these figures andwith continued reference to FIGS. 69-71.

In an embodiment, routing insulator 560 is provided with similarstructure as routing insulators 160 and 360 previously described forfundamentally the same purpose of providing electrically insulator thestator core 512 from the stator windings 514 at the rear end of themotor 500 and providing a support structure for the rear bearing bridge540. Further, in an embodiment, routing insulator 560 supports a seriesof stator terminals 590 projecting along the axial direction away fromthe stator assembly 510 for coupling to the circuit board assembly 580.In an embodiment, configuration of the stator terminals 590 and theirmounting to the routing insulator 560 may be in accordance with any ofthe embodiments previously described in this disclosure.

In an embodiment, routing insulator 560 includes a main cylindrical body562 having approximately an outer diameter that is approximately equalto or slightly smaller than the outer diameter of the stator core 512arranged to be received inside the rear opening of the motor can 502,and an annular lip 564 having approximately the same outer diameter asthe motor can 502 and arranged to rest in contact with the rear end ofthe motor can 502.

In an embodiment, routing insulator 560 additionally includes a seriesof peripheral openings 568 formed through the main cylindrical body 562.Retaining insert members 550 are received radially into peripheralopenings 568 during the assembly process and prior to insertion of themain cylindrical body 562 into the motor can 502. In an embodiment, eachretaining insert member 550 includes a fastening receptacle 554 thatextends along the axial direction of the motor 500. After insertion ofthe main cylindrical body 562 into the motor can 502, the retaininginsert members 550 are securely held inside the peripheral openings 568against the inner surface of the motor can 502. In this position, thefastening receptacle 554 are positioned radially inward of the annularlip 564 and are therefore accessible along the axial direction.

In an embodiment, the routing insulator 560 further includes a series ofside cut-out regions 566 that extend between adjacent stator terminals590 through the annular lip 564 to the rear end of the routing insulator560. In an embodiment, cut-out regions 566 and peripheral openings 568are alternatingly disposed.

In an embodiment, rear bearing bridge 540 includes a cylindrical body542 forming a bearing pocket for securely receiving an outer race of therear bearing 506. In an embodiment, the sense magnet 507 is positionedwithin the cylindrical body 542 with an airgap in between so it is notin physical contact with the rear bearing bridge 540.

In an embodiment, rear bearing bridge 540 further includes a series ofside protrusions 544 extending radially outwardly from the outer surfaceof the cylindrical body 542. The rear bearing bridge 540 is receivedwithin the body of the routing insulator 560 to position the rearbearing 506 and the sense magnet 507 substantially radially inward ofthe routing insulator 560. The side protrusions 544 pilot and supportthe rear bearing bridge 540 to routing insulator 560, with at leastouter walls of the side protrusions 544 being slidingly and securelyreceived within cut-out regions 566. In this manner, the rear bearingbridge 540 is structurally supported and piloted to the routinginsulator 560 along the radial and circumferential directions. In anembodiment, the outer wall of each side protrusion 544 includes astepped profile to form a substantially flush outer body with the outersurfaces of the cylindrical body 542 and the annular lip 564 of therouting insulator 540. This allows the front portions of the outer wallsof the side protrusion 544 to also be supported in contact with themotor can 502 to radially support and pilot the rear bearing bridge 540relative to the motor can 502.

In an embodiment, rear bearing bridge 540 further includes a series ofside arms 546 extending radially outwardly from a rear end of thecylindrical body 542. In an embodiment, side protrusions 544 and sidearms 546 are alternatingly disposed around the cylindrical body 542. Inan embodiment, side arms 546 are oriented to rest on the rear end of theannular lip 564 of the routing insulator 560 between pairs of adjacentstator terminals 590. Further, in an embodiment, side arms 546 includethrough-holes 547 located radially inward of the annular lip 564 andaxially in-line with the fastening receptacles 554 of the retaininginsert members 550. A series of fasteners 548 are axially receivedthrough the through-holes 547 and fastened into the fasteningreceptacles 554. In this manner, the rear bearing bridge 540 isstructurally supported and piloted to the routing insulator 560 alongthe axial direction.

In an embodiment, rear bearing bridge 540 further includes a series offastening receptacles 545 formed through one or more of the sideprotrusions 544 along the axial direction. Fastening receptacles 545 areprovided for securing the circuit board assembly 580 to the routinginsulator 540.

In an embodiment, circuit board assembly 580 includes many of the samefeatures as the previously-described circuit board assembly 380,including a circuit board 582 accommodating magnetic sensors and tracesfor interconnecting the stator terminals 590, peripheral slots 586 forreceiving the stator terminals 590, power wires 589 for supplyingelectric power to the motor 500, and a series of signal wires 588 forcommunication between a microcontroller and the magnetic sensors. In anembodiment, circuit board assembly 580 also includes an overmoldstructure 581 formed around at least the rear surface of the circuitboard 582. In an embodiment, circuit board assembly 580 is secured tothe fastening receptacles 545 of the routing insulator 540 via fasteners587.

Various embodiments of this invention described herein provide abrushless motor assembly suitable for use in a gripping handle of apower tool. The tables provided below highlights some of the power andsize advantage of the motor assembly.

Table 1 below outlines various size and power output parameters of sixexemplary motors A-F constructed according to the teachings above,according to exemplary embodiments. The six motors here include the samestator diameter of 30 mm, but different stator stack lengths (30 mm, 48mm, and 60 mm) and different permanent magnet grades (42H v. 56M). Themagnet grades are used by way of example to show the effect of usinghigher grade magnets in the motor. In an embodiment, the ring-magnetdesign may utilize a 42H magnet grade, and the surface-mount magnetdesign may utilize a 56H magnet grade.

TABLE 1 Motor A Motor B Motor C Motor D Motor E Motor F Stator Size (ODmm) 30 30 30 30 30 30 Stator Stack Length (mm) 30 48 60 30 48 60 MotorMagnetic Length (M_(MAG)) (mm) 43 61 73 43 61 73 Magnet Grade 42H 42H42H 56M 56M 56M Line-to-Line Motor Impedance (Ohm)-R 0.045 0.026 0.0200.037 0.022 0.015 Battery Nominal Voltage (V) 20 20 20 20 20 20 BatteryImpedance (mOhm) 62 62 62 62 62 62 Peak Power output (W)-P_(P) 500 700800 550 760 875 Continuous Power output (W)-P_(C) 375 550 675 400 570690 Peak Efficiency (%) 74% 76.2% 76.4% 73.5% 75.2% 74.7% Kt (at 50 A) =Torque per Amp 5.68 5.63 5.22 5.66 5.39 4.86 (Nmm/A) Km = Kt/√R (Nmm/√W)26.73 34.65 37.97 28.83 36.60 39.23 Peak Power/Stator Diameter (W/mm)16.7 23.3 26.7 18.3 25.3 29.2 Km/Stator Diameter (Nmm/√W)/mm 0.89 1.161.27 0.96 1.22 1.31

In these examples, a cross-sectional area of motors A-F, not includingthe motor can 302, is approximately 707 mm{circumflex over ( )}2. Acircumference of the motors A-F, not including the motor can 302, isapproximately 94.2 mm. In a canned motor design, the motor can 302includes a diameter of approximately 33 mm and a motor can circumferenceof approximately 103.6 mm. Using the canned motor design, the power toolhas a grip diameter of approximately 36 mm to 40 mm, preferably smallerthan or equal to approximately 42 mm, and a grip circumference ofapproximately to 113 mm to 127 mm, preferably smaller than or equal toapproximately 132 mm. In a clamshell motor design, the clamshell 402,which makes up the grip portion of the tool housing, includes a diameterof approximately 35 mm and a grip circumference of approximately 110 mm,preferably a diameter of less than or equal to 38 mm and a gripcircumference of less than or equal to approximately 120 mm.

In an embodiment, using a 20V max power tool battery pack having anominal voltage of approximately 18V, a battery capacity ofapproximately 5 amperes-per-hour, and a battery impedance ofapproximately 62 mOhms, motors A-C are capable of producing a maximumpower output of 500 to 800 watts and continuous (long duration) poweroutput of 375 to 675 watts depending on the stator stack size.Similarly, motors D-F can produce a maximum power output of 550 to 875watts and continuous (long duration) power output of 400 to 690 wattsdepending on the stator stack size. This represents approximately a 10%improvement in maximum power output and 2% to 5% increase in continuouspower output due to use of higher grade magnets. In an embodiment,motors A-F operate at an efficiency (i.e., power output/power output) ofgreater than equal to 74%.

In an embodiment, motors A-F produce a significant higher power outputand efficiency per unit of motor diameter, motor girth, and power toolgirth. In an embodiment, motors A-F, when using a 20V max battery packas described above, produce a maximum power output to stator diameterratio of at least 16.7 W/mm, which increases with larger stator stacklength and higher magnet grade. Similarly, motors A-F produce a maximumpower output to tool diameter ratio of at least 13.9 W/mm, and a maximumpower output to tool grip circumference of at least 4.5 W/mm.

Furthermore, in an embodiment, motors A-F yield a significantimprovement in the motor size (Km) constant as compared to conventionalmotors. As understood by those skilled in the art, the Km constant is aparameter for determining the efficiency and capacity of a motor. The Kmconstant is calculated as a function of the torque constant Kt and theresistance of the motor R, Km=Kt/√R ((Nmm/A)/√Ohm), or Km=Kt*I/P(Nmm/√W), where torque constant Kt is the torque produced divided bymotor current, R is the line-to-line impedance of the motor, and P isthe power in watts (W). Thus, the Km constant represents the capabilityof the motor to produce power normalized by resistance of the motor.Both the Km and Kt constants, and in particular ratios of the Km and Ktconstants to motor size parameters including motor diameter and motorgirth, were seen to significantly improve over conventional power toolmotors. In an embodiment, motors A-F include a motor constant (Km) tostator diameter of 0.89 to 1.31 (Nmm/√W)/mm. Similarly, motors A-Fproduce a motor constant to tool diameter ratio of at least 0.74(Nmm/√W)/mm, and a motor constant to tool grip circumference of at least0.24 (Nmm/√W)/mm.

As previously discussed, motor 300 includes a sense magnet ring 307 thatmagnetically interacts with Hall sensors mounted on the circuit board382. Table 2 below summarizes, for a motor according to thisconfiguration, the motor length M (see FIG. 27), as defined from a rearend of the circuit board 382 to the front end of the front bearingbridge 330; a non-magnetic length of the motor, as the part of the motoroutside the magnetic length MMAG; and the motor volume V.

TABLE 2 MOTOR WITH SENSE MAGNET Motor A Motor B Motor C Motor D Motor EMotor F Motor Length (M) (mm) 67.05 85.25 97.15 67.05 85.25 97.15Non-Magnetic Length M-M_(MAG) (mm) 24 24 24 24 24 24 Km/M Ratio(Nmm/√W)/mm 0.40 0.41 0.39 0.43 0.43 0.40 Peak Power/M Ratio (W/mm) 7.58.2 8.2 8.2 8.9 9.0 Motor Volume (V) (mm³) 47,395 60,260 68,671 47,39560,260 68,671 Km/V ((Nmm/√W)/mm³) 0.00056 0.00058 0.00055 0.000610.00061 0.00057 Peak Power/V Ratio (W/mm³) 0.0105 0.0116 0.0116 0.01160.0126 0.0127

In an embodiment, it is possible for motor 300 to be configured withoutthe sense magnet ring 307. This may be done in a, for example, asensorless motor control implementation, where the rotational positionof the motor is detected via the controller by monitoring the back-EMFof the motor in a trapezoidal control scheme, or the motor current in afield-orientated control scheme. Alternatively, motor 300 may beconfigured to allow direct sensing of the rotor magnets 326 by the Hallsensors, thus eliminating the need for the sense magnet ring 307. Ineither configuration, the length of the rear bearing bridge 340 and therouting insulator 360 may be shortened by approximately 10 to 12 mm.Table 3 below summarizes, for a motor according to this configuration,the motor length M′, the non-magnetic length of the motor, and the motorvolume V′.

TABLE 3 MOTOR WITHOUT SENSE MAGNET Motor A Motor B Motor C Motor D MotorE Motor F Motor Length (M′) (mm) 55.8 74 85.9 55.8 74 85.9 Non-MagneticLength M′-M_(MAG) (mm) 13 13 13 13 13 13 Km/M′ (Nmm/√W)/mm 0.48 0.470.44 0.52 0.49 0.46 Peak Power/M′ (W/mm) 9.0 9.5 9.3 9.9 10.3 10.2 MotorVolume (V′) (mm³) 39,443 52,308 60,719 39,443 52,308 60,719 Km/V′((Nmm/√W)/mm³) 0.00068 0.00066 0.00063 0.00073 0.00070 0.00065 PeakPower/V′ Ratio (W/mm³) 0.0127 0.0134 0.0132 0.0139 0.0145 0.0144

In an embodiment, as shown in Tables 2 and 3, a ratio of the maximumpower output to the motor length is in the range of approximately 7.5 to10.2 W/mm, and a ratio of the maximum power output to the volume of themotor is approximately 0.0105 to 0.0145 W/mm³. In an embodiment, a ratioof the motor constant Km to the motor length is in the range ofapproximately 0.39 to 0.52 (Nmm/√W)/mm, and a ratio of the motorconstant Km to the volume of the motor is approximately 0.00055 to0.00070 (Nmm/√W)/mm³.

Table 4 below outlines various size and power output parameters of sixexemplary motors G-I constructed according to the teachings of thisdisclosure, according to exemplary embodiments. The three motors hereare provided with a larger diameter than motors A-F discussed above. Thethree motors include the same stator diameter of 32 mm and the samemagnet grade (56M), but different stator stack lengths (25 mm, 40 mm,and 60 mm). Furthermore, motors G-I are tested using two separatebattery packs—a 20V max 62 mOhm battery pack (first three rows), and 20Vmax lower impedance 18 mOhm battery pack (second three rows), toillustrate the effects of the impedance of the battery pack on outputpower of the motor.

TABLE 4 Motor G Motor H Motor I Motor G Motor H Motor I Stator Size (ODmm) 32 32 32 32 32 32 Stator Stack Length (mm) 25 40 60 25 40 60 MotorMagnetic Length (M_(MAG)) (mm) 38 53 73 38 53 73 Magnet Grade 56M 56M56M 56M 56M 56M Motor Impedance (line-line) 0.034 0.019 0.012 0.0340.019 0.012 Battery Nominal Voltage (V) 20 20 20 20 20 20 BatteryImpedance (mOhm) 62 62 62 18 18 18 Peak Power output (W)-P_(P) 560 780950 800 1200 1550 Continuous Power output (W)-P_(C) 400 585 730 415 640830 Peak Efficiency (%) 74.1% 75.8% 76% 73.8% 75.6% 76% Kt (at 50 A) =Torque per Amp 5.7 5.5 5.0 5.7 5.5 5.0 (Nmm/A) Km = Kt/√R (Nmm/√W) 31 4046 31 40 46 Peak Power/Stator Diameter (W/mm) 17.5 24.4 29.7 25.0 37.548.4 Km/Stator Diameter (Nmm/√W)/mm 0.97 1.25 1.44 0.97 1.25 1.44

In these examples, a cross-sectional area of motors G-I, not includingthe motor can 302, is approximately 804 mm{circumflex over ( )}2. Acircumference of the motors G-I, not including the motor can 302, isapproximately 100.5 mm. In a canned motor design, the motor can 302includes a diameter of approximately 35 mm and a motor can circumferenceof approximately 110 mm. Using the canned motor design, the power toolhas a grip diameter of approximately 38 mm to 42 mm, preferably smallerthan or equal to approximately 44 mm, and a grip circumference ofapproximately to 120 mm to 132 mm, preferably smaller than or equal toapproximately 138 mm. In a clamshell motor design, the clamshell 402,which makes up the grip portion of the tool housing, includes a diameterof approximately 37 mm and a grip circumference of approximately 116 mm.

In an embodiment, using a 20V max power tool battery pack having anominal voltage of approximately 18V, a battery capacity ofapproximately 5 amperes-per-hour, and a battery impedance ofapproximately 62 mOhms, motors G-I are capable of producing a maximumpower output of 560 to 950 watts and continuous (long duration) poweroutput of 400 to 730 watts depending on the stator stack size. Whenusing a higher impedance battery pack, motors G-I can produce a maximumpower output of 800 to 1550 watts and continuous (long duration) poweroutput of 415 to 830 watts depending on the stator stack size. In anembodiment, motors G-I operate at an efficiency (i.e., poweroutput/power output) of greater than equal to 74%.

In an embodiment, motors G-I produce a maximum power output to statordiameter ratio of at least 17.5 W/mm, which increases with larger statorstack length and higher magnet grade. Similarly, motors G-I produce amaximum power output to tool diameter ratio of at least 15.1 W/mm, and amaximum power output to tool grip circumference of at least 4.8 W/mm.

Furthermore, in an embodiment, motors G-I yield a significantimprovement in the motor size (Km) constant as compared to conventionalmotors. In an embodiment, motors G-I include a motor constant (Km) tostator diameter of 0.97 to 1.44 (Nmm/√W)/mm. Similarly, motors A-Fproduce a motor constant to tool diameter ratio of at least 0.83(Nmm/√W)/mm, and a motor constant to tool grip circumference of at least0.26 (Nmm/√W)/mm.

Table 5 below summarizes the motor length M, a non-magnetic length ofthe motor, and the motor volume V, for motors G-I configured to includea sense magnet ring 307.

TABLE 5 MOTOR WITH SENSE MAGNET Motor G Motor H Motor I Motor G Motor HMotor I Motor Length (M) (mm) 65.6 80.65 100.6 65.6 80.65 100.6Non-Magnetic Length M-M_(MAG) (mm) 27.6 27.6 27.6 27.6 27.6 27.6 Km/MRatio (Nmm/√W)/mm 0.47 0.50 0.46 0.47 0.50 0.46 Peak Power/M Ratio(W/mm) 8.5 9.7 9.4 12.2 14.9 15.4 Motor Volume (V) (mm³) 52,759 64,86380,907 52,759 64,863 80,907 Km/V ((Nmm/√W)/mm³) 0.00059 0.00062 0.000570.00059 0.00062 0.00057 Peak Power/V Ratio (W/mm³) 0.0106 0.0120 0.01170.0152 0.0185 0.0192

Table 6 below summarizes the motor length M, a non-magnetic length ofthe motor, and the motor volume V, for motors G-I configured without asense magnet ring 307.

TABLE 6 MOTOR WITHOUT SENSE MAGNET Motor G Motor H Motor I Motor G MotorH Motor I Motor Length (M′) (mm) 53.5 68.55 88.5 53.5 68.55 88.5Non-Magnetic Length M′-M_(MAG) (mm) 15.5 15.5 15.5 15.5 15.5 15.5 Km/M′(Nmm/√W)/mm 0.58 0.59 0.52 0.58 0.59 0.52 Peak Power/M′ (W/mm) 10.5 11.410.7 15.0 17.5 17.5 Motor Volume (V′) (mm³) 43,027 55,131 71,176 43,02755,131 71,176 Km/V′ ((Nmm/√W)/mm³) 0.00072 0.00073 0.00065 0.000720.00073 0.00065 Peak Power/V′ Ratio (W/mm³) 0.0130 0.0141 0.0133 0.01860.0218 0.0218

In an embodiment, as shown in Tables 5 and 6, a ratio of the maximumpower output to the motor length is in the range of approximately 8.5 to17.5 W/mm, and a ratio of the maximum power output to the volume of themotor is approximately 0.0106 to 0.0218 W/mm³. In an embodiment, a ratioof the motor constant Km to the motor length is in the range ofapproximately 0.46 to 0.59 (Nmm/√W)/mm, and a ratio of the motorconstant Km to the volume of the motor is approximately 0.00059 to0.00073 (Nmm/√W)/mm³.

While the examples above are made for a 30 mm and a 32 mm statordiameter, it should be understood that a stator diameter of up to 34 mmis within the scope of this disclosure.

Two alternative embodiments of a circuit board and its connectivity tothe stator windings is described herein with reference to FIGS. 77-80.While the embodiments described above include stator terminals supportedby the routing insulator to facilitate connections between the magnetwire and the circuit boards, the embodiments described below utilizedirect electrical connections between the circuit board and the magnetwire.

FIG. 77 depicts a perspective view of a routing insulator 660 disposedat the end of the stator assembly 610, according to an embodiment.

As shown in these figures, in an embodiment, routing insulator 660includes a main cylindrical body 662 and a series of arms 664 extendingaxially from the main body 662 between stator windings 616 of the statorassembly 610. Cross-over portions 618 of the magnet wire forming thestator windings 616 are routed along the sides of the arms 664 andguided along an outer surface of an upper portion 666 of the arms 664.In an embodiment, each arm 664 includes two side recesses 668 formedalong its axial edges proximate the upper portion 666.

FIG. 78 depicts a perspective view of a circuit board 680 mounted on therouting insulator 660, according to an embodiment.

In an embodiment, the circuit board 680 includes a series of peripheralprojections 682 sized to be received into gaps between the arms 664 andare snap-fit into the side recesses 668 of the arms 664. Cross-overportions 618 of the magnet wire comes into direct contact with thecircuit board 680 at or near the points of contact between theperipheral projections 682 and the recesses 668. The circuit board 680includes proper conductive traces that make electrical connections withthe cross-over portions 618 at the points of contact. This arrangementallows the circuit board 680 to facilitate interconnections between thestator windings 616 using direct connections to the magnet wire andwithout a need for resistance welding connections using intermediarystator terminals.

FIG. 79 depicts a perspective view of a circuit board 780 mounted on arouting insulator 760 of a stator assembly 710, according to analternative embodiment. FIG. 80 depicts a partial cross-sectional viewof the circuit board 780 and the routing insulator 760, according to anembodiment.

As shown in these figures, in an embodiment, routing insulator 760includes a main cylindrical body 762 and a series of arms 764 extendingaxially from the main body 762 between stator windings (not shown) ofthe stator assembly 710. Each arm 764 includes two axial posts 766extending from its rear end. Cross-over portions 718 of the magnet wireforming the stator windings 616 are routed partially along the sides ofthe arms 764 and guided in contact with the axial posts 766 and throughthe gaps formed on each arm 764 between the axial posts 766.

In an embodiment, circuit board 780 is mounted on the routing insulator760 in contact with the axial posts 766 and secured to the routinginsulator 760 via a series of fasteners 782. The circuit board 780 isoriented so a plane formed by the circuit board 782 intersects the gapsformed between the axial posts 766 of the arms 764. In an embodiment, aseries of conductive tabs 784 are mounted on the circuit board 780 nearits outer edge. Each conductive tab 784 includes a first portion 786that is mounted on the circuit board 780 and in electrical contact witha conductive trace of the circuit board 780, and a second portion 788that extends approximately perpendicularly from the first portion 786and is received inside the gap formed between the axial posts 766 of thearms 764. The cross-over portions 718 of the magnet wire areelectrically coupled, e.g., via soldering, ultrasonic welding, or otherknown metal-to-metal bonding technique, to the second portions 788 ofthe conductive tabs 784 within each gap. This arrangement allows thecircuit board 780 to facilitate interconnections between the statorwindings using direct connections to the magnet wire and without a needfor intermediary stator terminals.

Example embodiments have been provided so that this disclosure will bethorough, and to fully convey the scope to those who are skilled in theart. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Terms of degree such as “generally,” “substantially,” “approximately,”and “about” may be used herein when describing the relative positions,sizes, dimensions, or values of various elements, components, regions,layers and/or sections. These terms mean that such relative positions,sizes, dimensions, or values are within the defined range or comparison(e.g., equal or close to equal) with sufficient precision as would beunderstood by one of ordinary skill in the art in the context of thevarious elements, components, regions, layers and/or sections beingdescribed.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

1. A power tool comprising: a housing including a grip portion having a grip circumference of smaller than or equal to approximately 120 mm; and a brushless direct-current (BLDC) motor at least partially disposed within the grip portion of the housing and configured to output a maximum power output of at least 450 watts, the motor comprising: a stator including a stator core and a plurality of stator windings; and a rotor rotatably received within the stator and including a rotor shaft extending along a longitudinal axis and a plurality of permanent magnet rings mounted sequentially oriented along the longitudinal axis and surrounding the rotor shaft, each permanent magnet including a plurality of magnetic poles.
 2. The power tool of claim 1, wherein the rotor includes an outer diameter in the range of approximately 13 mm to 16 mm and a length that is at least 1.4 times greater than the outer diameter.
 3. The power tool of claim 1, wherein the rotor further comprises a plurality of rotor core segments securely mounted in series on the rotor shaft, the plurality of permanent magnet rings being respectively mounted on the plurality of rotor core segments.
 4. The power tool of claim 3, wherein each rotor core segment is provided with at least two annular alignment members comprising flexible material mounted proximate two ends of the rotor core segment between the rotor core segment and the corresponding permanent magnet ring.
 5. The power tool of claim 3, wherein each rotor core segment includes a plurality of annular grooves, wherein an adhesive material is disposed within the plurality of annular grooves for retention of the corresponding permanent magnet ring.
 6. The power tool of claim 1, wherein the plurality of permanent magnet rings is securely mounted directly on the rotor shaft.
 7. The power tool of claim 1, wherein the rotor shaft includes a stepped construction including a first portion surrounded by the plurality of permanent magnet rings and having a first diameter, and a second portion not surrounded by the plurality of permanent magnet rings and having a second diameter, wherein the first diameter is greater than the second diameter.
 8. The power tool of claim 7, wherein the motor further comprises a rotor bearing mounted on the second portion of the rotor shaft, and a circuit board electrically coupled to the plurality of stator windings and including a plurality of conductive traces facilitating interconnections between the plurality of stator windings, wherein the rotor bearing is located between the plurality of permanent magnet rings and the circuit board along the longitudinal axis.
 9. The power tool of claim 8, wherein the motor further comprises a front bearing mounted on the rotor shaft forward of the rotor assembly.
 10. A power tool comprising: a housing; and a brushless direct-current (BLDC) motor disposed within the housing, the motor comprising: a stator including a stator core and a plurality of stator windings; and a rotor rotatably received within the stator and including a rotor shaft extending along a longitudinal axis and a plurality of permanent magnets, wherein the rotor shaft includes a stepped construction including a first portion inside the stator assembly having a first diameter and a second portion outside the stator assembly having a second diameter, wherein the first diameter is greater than the second diameter and the plurality of permanent magnets is mounted directly on the first portion of the rotor shaft.
 11. The power tool of claim 10, wherein the motor further comprises a magnet ring integrally including the plurality of permanent magnets, the magnet ring having an inner diameter that is approximately equivalent to the first diameter of the rotor shaft so as to be securely mounted on the first portion of the rotor shaft.
 12. The power tool of claim 11, wherein the magnet ring comprises a plurality of magnet rings mounted in series on the first portion of the rotor shaft.
 13. The power tool of claim 10, wherein the motor further comprises a rotor bearing mounted on the second portion of the rotor shaft, and a circuit board electrically coupled to the plurality of stator windings and including a plurality of conductive traces facilitating interconnections between the plurality of stator windings, wherein the rotor bearing is located between the plurality of permanent magnet rings and the circuit board.
 14. The power tool of claim 13, wherein the motor further comprises a sense magnet mounted on the second portion of the rotor shaft, wherein the circuit board includes a plurality of Hall sensors in magnetic interface with the sense magnet.
 15. A power tool comprising: a housing; and a brushless direct-current (BLDC) motor disposed within the housing, the motor comprising: a stator including a stator core and a plurality of stator windings; a rotor rotatably received within the stator and including a rotor shaft extending along a longitudinal axis and a plurality of permanent magnets; a bearing bridge including a center pocket formed around the rotor shaft, wherein a rotor bearing mounted on the rotor shaft is securely received within the center pocket; and a circuit board electrically coupled to the plurality of stator windings and including a plurality of conductive traces facilitating interconnections between the plurality of stator windings, wherein the rotor bearing is located between the plurality of permanent magnets and the circuit board along the longitudinal axis.
 16. The power tool of claim 15, wherein the motor further includes an end insulator configured to electrically insulate the stator core from the plurality of stator windings and including an annular body extending away from the stator core, wherein the bearing bridge is received at least partially within the end insulator.
 17. The power tool of claim 16, wherein the plurality of stator windings is wound from a continuous magnet wire having cross-over portions extending between the adjacent stator windings, wherein the cross-over portions are guided in contact with the end insulator to be electrically coupled to the circuit board, wherein a radial plane formed through the rotor bearing intersects the cross-over portions.
 18. The power tool of claim 17, wherein the motor further includes a plurality of stator terminals mounted on the end insulator and oriented circumferentially outward of an end of the bearing pocket, the plurality of stator terminals including first portions arranged to receive the cross-over portions and second portions arranged to be secured to the circuit board to electrically couple the cross-over portions of to the circuit board.
 19. The power tool of claim 16, wherein a radial plane formed through the rotor bearing intersects the annular body of the end insulator.
 20. The power tool of claim 15, wherein the motor further includes a sense magnet mounted on the second portion of the rotor shaft, wherein the circuit board includes a plurality of Hall sensors in magnetic interface with the sense magnet. 